HEREDITY  AND  EUGENICS 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 

Bgenta 
THE  BAKER  &  TAYLOR  COMPANY 

NEW    YORK 

THE  CAMBRIDGE  UNIVERSITY  PRESS 

LONDON    AND    EDINBURGH 


HEREDITY  AND  EUGENICS 


A  COURSE  OF  LECTURES  SUMMARIZING  RECENT  ADVANCES  IN  KNOWLEDGE 
IN  VARIATION,  HEREDITY.  AND  EVOLUTION  AND  ITS  RELATION 
TO  PLANT,  ANIMAL.  AND  HUMAN  IMPROVE- 
MENT AND  WELFARE 

BY 

WILLIAM  ERNEST  CASTLE 

JOHN  MERLE  COULTER 
CHARLES  BENEDICT  DAVENPORT 

EDWARD  MURRAY  EAST 
WILLIAM  LAWRENCE  TOWER 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 


COPYRIGHT  1912  BY 
THE  UNIVERSITY  OF  CHICAGO 


All  Rights  Reserved 


Published  June  1912 
Second  Impression  January  1913 


Composed  and  Printed  By 

The  University  of  Chicago  Press 

Chicago,  Illinois.    U.S.A. 


PREFACE 

During  the  summer  of  1911,  a  course  of  lectures  on 
heredity  and  allied  topics  was  given  at  the  University  of 
Chicago,  under  the  auspices  of  the  biological  departments. 
The  purpose  of  the  course  was  to  present  the  recent  develop- 
ments of  knowledge  in  reference  to  variation,  heredity,  and 
evolution,  and  the  application  of  this  new  knowledge  to 
plant,  animal,  and  human  development  and  improvement. 

The  lectures  were  not  intended  for  those  trained  in 
biology,  but  for  a  general  university  audience,  interested 
in  the  progress  of  genetics  as  a  matter  of  information  rather 
than  of  study.  The  lecturers,  therefore,  did  not  address 
themselves  to  their  colleagues,  and  did  not  attempt  to 
include  any  considerable  amount  of  new  material.  It  is 
believed  that  a  much  larger  audience  than  the  one  originally 
addressed  might  be  interested  in  this  summary  of  results 
in  one  of  the  important  and  recently  cultivated  fields  of 
biology,  and  therefore  this  volume  has  been  published. 
It  is  hoped  that  it  may  perform  a  service  not  only  for  those 
interested  in  biology  as  a  field  outside  their  own  experience, 
but  also  for  those  biologists  whose  work  deals  with  other 
phases  of  biology. 

The  lectures  were  given  by  five  lecturers,  with  no  oppor- 
tunity to  relate  the  lectures  to  one  another  other  than  as 
suggested  by  the  assigned  titles.  It  is  inevitable  that  there 
should  be  more  or  less  overlapping  of  statements,  and  no 
attempt  has  been  made  to  avoid  this.  Each  lecture, 
therefore,  is  complete  in  itself,  as  it  was  delivered. 


1117018 


vi  Preface 

No  attempt  has  been  made  to  include  the  whole  of  the 
fields  represented  by  the  general  topics.  The  plan  was  to 
select  certain  representative  investigators  to  speak  of  their 
work.  Four  such  investigators  were  selected,  the  mission 
of  the  fifth  lecturer  being  to  give  the  elementary  information 
(chaps,  i  and  ii)  necessary  for  an  audience  untrained  in  biology, 
and  thus  to  prepare  the  way  for  the  more  special  topics. 

It  is  hoped  that  similar  series  of  lectures  in  other  fields 
of  biology  will  be  given  during  successive  summers,  and 
that  the  present  volume  may  be  the  first  of  a  series  which  will 
represent  the  most  significant  aspects  of  current  biological 
investigation. 

J.   M.  COULTER 
F.  R.  LILLIE 
W.  L.  TOWER 


TABLE  OF  CONTENTS 

CHAPTER  PAGE 

I.  RECENT  DEVELOPMENTS  IN  HEREDITY  AND  EVOLUTION: 
GENERAL  INTRODUCTION     ..'.....        3 

II.  THE  PHYSICAL  BASIS  OF  HEREDITY  AND  EVOLUTION 
FROM  THE  CYTOLOGICAL  STANDPOINT       .       .       .       .       22 

JOHN  MERLE   COULTER,   Professor  and  Head  of  the 
Department  of  Botany,  the  University  of  Chicago 


III.  THE  METHOD  OF  EVOLUTION 39 

IV.  HEREDITY  AND  SEX 62 

WILLIAM  ERNEST  CASTLE,  Professor  of  Zoology,  Har- 
vard University 


V.    INHERITANCE  IN  THE  HIGHER  PLANTS    ....       83 

VI.    THE  APPLICATION  OF  BIOLOGICAL  PRINCIPLES  TO  PLANT 

BREEDING      ; 113 

EDWARD  MURRAY  EAST,  Assistant  Professor  of  Experi- 
mental Plant  Morphology,  Harvard  University 


VII.  RECENT  ADVANCES  AND  THE  PRESENT  STATE  OF  KNOWL- 
EDGE CONCERNING  THE  MODIFICATION  OF  THE  GER- 
MINAL CONSTITUTION  OF  ORGANISMS  BY  EXPERIMENTAL 

PROCESSES     . 141 

WILLIAM  LAWRENCE  TOWER,    Associate    Professor   of 
Zoology,  the  University  of  Chicago 


VIII.    THE  INHERITANCE  OF  PHYSICAL  AND  MENTAL  TRAITS 

OF  MAN  AND  THEIR  APPLICATION  TO  EUGENICS    .       .     269 

IX.    THE  GEOGRAPHY  OF  MAN  IN  RELATION  TO  EUGENICS   .     289 

CHARLES  BENEDICT  DAVENPORT,  Station  for  Experimen- 
tal Evolution,  Carnegie  Institution  of  Washington 

INDEX 313 


JOHN  MERLE  COULTER 

Professor  and  Head  of  the  Department  of  Botany 
The  University  of  Chicago 


CHAPTER  I 

RECENT  DEVELOPMENTS  IN  HEREDITY  AND 
EVOLUTION:  GENERAL  INTRODUCTION 

This  series  of  lectures  is  intended  to  present,  in  outline, 
the  recent  development  of  knowledge  in  reference  to  heredity 
and  evolution.  These  subjects  have  to  do,  not  only  with 
the  most  fundamental  conceptions  of  biology,  but  they  have 
come  to  be  of  immense  practical  importance  in  animal  and 
plant  breeding.  From  every  aspect,  therefore,  they  appeal 
to  all  persons  intelligent  enough  to  be  interested  in  the 
progress  of  knowledge  and  in  human  welfare.  At  the  same 
time,  it  is  recognized  that  most  people  are  denied  the  oppor- 
tunity of  knowing  the  progress  that  has  been  made  in  these 
subjects,  through  lack  of  biological  training  or  lack  of  time. 
To  them  the  suggestions  of  progress  have  come  chiefly 
through  ephemeral  and  often  misleading  publications. 

It  is  the  purpose  of  this  series,  therefore,  to  present  this 
information  in  such  a  form  that  it  can  be  appreciated  by 
those  who  have  no  special  training  in  biological  work ;  in  short, 
to  interpret  the  significant  results  of  recent  investigations. 

Before  presenting  the  recent  developments  in  the  inves- 
tigation of  heredity  and  evolution,  it  is  essential  to  provide 
a  historical  background,  for  nothing  is  more  obvious  than 
that  the  work  of  today  has  evolved  gradually  from  all  the 
work  of  the  past.  It  should  be  understood,  also,  that  the 
subject  is  so  vast  in  scope  and  in  work  that  to  outline  it  in 
a  few  lectures  will  require  the  most  rigid  selection  of  material, 
a  selection  so  rigid  that  students  of  the  subject  will  be  able 
to  point  out  glaring  omissions. 


4  Heredity  and  Eugenics 

If  rigid  selection  is  necessary  in  presenting  the  recent 
work,  it  must  be  still  more  rigid  in  sketching  the  historical 
background,  with  its  enormous  literature,  stretching  through 
many  years.  Probably  no  two  biologists  would  put  the 
same  details  into  the  background,  but  probably  all  of  them 
would  give  the  background  the  same  general  aspect;  for 
it  is  more  of  an  atmosphere  than  detail  that  is  needed.  It 
will  be  an  aid  to  understanding  and  to  memory  if  this 
sketch  is  broken  up  into  distinct  topics,  if  it  be  understood 
clearly  that  there  are  no  such  natural  lines  of  cleavage  in 
the  subject. 

I.   THE  CONCEPTION  OF  EVOLUTION 

Those  who  know  of  the  theory  of  evolution  only  in  a 
superficial  way,  as  a  thing  heard  of  rather  than  understood, 
almost  invariably  associate  it  with  some  man  who  stands 
to  them  as  its  author.  In  my  own  experience,  I  have 
encountered  a  widespread  conviction  that  Darwin  is  respon- 
sible for  the  theory  of  organic  evolution.  The  fact  is  that 
the  conception  of  evolution,  both  inorganic  and  organic,  is 
as  old  as  our  record  of  man 's  thought,  and  therefore  no  one 
is  responsible  for  it.  It  is  the  common  property  of  the 
human  race. 

However,  a  sharp  distinction  must  be  made  between  the 
speculative  stage  of  evolution  and  the  observational  stage. 
The  former  is  imaginative  or  philosophical,  and  could  not 
establish  evolution  as  a  fact;  the  latter  is  scientific,  and  has 
established  evolution  as  a  fact.  In  a  real  sense,  therefore, 
organic  evolution  as  a  definite  working  principle  is  compara- 
tively modern,  being  but  little  more  than  one  hundred 
years  old. 


Recent  Developments  in  Heredity  and  Evolution  5 

2.     THE.  FACT  OF  EVOLUTION 

It  may  be  helpful  to  indicate  some  of  the  things  that 
began  to  open  the  eyes  of  thinking  men  and  finally  compelled 
them  to  accept  organic  evolution  as  a  fact. 

1.  The  growing  proof  that  the  inorganic  world  had  been 
formed  by  a  process  of  slow  evolution  rather  than  by  a 
series  of  miraculous  catastrophes,  compelled  the  suggestion 
that  the  organic  world  may  have  developed  in  the  same 
gradual  way  by  natural  processes. 

2.  The  observed  intergrading  of  species,  frequently  so 
complete  as  to  make  distinct  boundaries  for  species  impos- 
sible, strongly  suggested  the  passing  of  one  into  the  other. 
Dr.  Asa  Gray  once  remarked  that  he  did  not  believe  there 
are  any  species  of  North  American  asters,  although  he  had 
been  studying  them  for  twenty  years.     Of  course  this  was 
an  expression  of  despair  rather  than  of  belief,  but  it  illus- 
trates the  situation.     Botanists  for  a  long  time  emphasized 
the  boundaries  of  species  by  preserving  in  their  herbaria 
what  they  called  "typical  specimens"  and  discarding  the 
intergrades,  so  that  in  turning  over  the  sheets  of  a  herbarium 
the  species  looked  quite  distinct;    but  any  excursion  into 
the  field  brought  trouble. 

3.  Observations  began  to  multiply  showing  that  plants 
and  animals  are  often  able  to  respond  to  changed  con- 
ditions and  change  their  own  form  or  structure.     This 
was  called  the  power  of  "adaptation,"  and  it  has  been 
a  most  persistent  idea.     The  fact  of  change  was  evident, 
but  its  explanation  has  been  outgrown.     But  taking  it 
as  a  fact,  it  was  evident  that  the  small  changes  observed 
would    suggest    the    possibility    of    indefinitely    extended 
changes. 


6  Heredity  and  Eugenics 

4.  More  intimate  knowledge  of  the  structure  of  plant 
and  animal  bodies  revealed  what  were  called  "  rudimentary  " 
structures,  which  are  quite  evidently  abandoned  structures. 
This  suggested  at  once  that  they  were  functioning  structures 
hi  the  ancestral  forms.     Even  man,  and  perhaps  man  most 
of  all,  was  recognized  as  being  a  walking  museum  of  antiquity. 

5.  Then   the  life  panorama  of  the   geological    record 
began  to  be  unrolled ;  and  it  became  clear  that  a  fauna  and 
a  flora  totally  unlike  that  of  today  existed  in  the  earliest 
periods;    that  as  one  approached  the  later  records,  resem- 
blances began  to  appear;    and  that  insensibly  the  fauna 
and  flora  of  the  ancient  world  merged  into  those  of  today. 
This  was  historical  evidence  of  tremendous  weight  in  favor 
of  the  fact  of  a  gradual  organic  evolution. 

6.  Soon  what  is  called  embryology  began  to  be  studied, 
and  plants  and  animals  were  traced,  stage  by  stage,  from 
the  egg  to  the  adult  form.     In  the  course  of  this  develop- 
ment resemblances  to  other  forms  appeared,  which  had 
disappeared  when  the  adult  stage  was  reached.     And  so 
the  idea  developed  that  here  were  glimpses  of  earlier  con- 
nections, and  it  became  formulated  in  the  well-worn  state- 
ment that  the  history  of  the  individual  repeats  the  history 
of  the  race,  a  theory  labeled  "recapitulation." 

7.  Men's  eyes  also  began  to  be  opened  to  the  fact  that 
great  changes  had  been  wrought  in  plants  by  cultivation, 
and  in  animals  by  domestication ;  so  great  in  many  cases  that 
the  wild  originals  could  not  be  recognized  with  certainty. 
Later,  Darwin  called  this  "an  experiment  upon  a  gigantic 
scale,"  but  it  was  an  experiment  unconsciously  performed. 
At  least  it  proved  that  the  operations  of  man  could  modify 
plants  and  animals,  and  modify  them  so  much  that  resem- 
blances to  the  wild  originals  would  be  obscured. 


Recent  Developments  in  Heredity  and  Evolution  7 

The  seven  categories  of  facts  thus  indicated,  and  others 
that  might  be  added  to  them,  will  explain  why  a  number 
of  scientific  men  were  so  impressed  by  the  idea  that  organic 
evolution  is  a  fact,  that  they  thought  it  important  to 
search  for  an  explanation  of  the  process. 

3.   THE  EXPLANATION  OF  EVOLUTION 

To  accept  organic  evolution  as  a  fact,  and  to  explain 
it  as  a  process  are  two  very  different  things,  and  must  be 
kept  clearly  distinct.  The  failure  to  distinguish  them  has 
led  recently  to  much  confusion  in  popular  statement  and 
belief.  For  example,  the  more  exact  work  of  recent  years 
has  developed  a  considerable  body  of  criticism  against 
Darwin 's  theory  of  natural  selection.  To  those  who  thought 
of  the  theory  of  organic  evolution  as  belonging  to  Darwin, 
these  criticisms  seemed  to  indicate  that  belief  in  organic 
evolution  was  tottering;  when  in  fact,  if  any  belief  was 
tottering,  it  was  a  belief  in  natural  selection  as  a  sufficient 
explanation  of  the  process  of  evolution.  Darwin 's  explana- 
tion, Lamarck's  explanation,  every  explanation  hitherto 
proposed,  may  be  found  inadequate,  and  still  organic 
evolution  will  remain  to  be  explained.  It  must  be  remem- 
bered that  the  work  of  biologists  has  been  to  explain  the 
fact  of  organic  evolution,  not  to  propose  it  as  an  idea;  and 
the  destruction  of  no  explanation  can  weaken  the  fact. 

A  single  address  does  not  permit  the  mention  of  all  the 
proposed  explanations  of  organic  evolution,  but  a  few  domi- 
nating ones  may  be  selected  as  illustrations.  The  selection 
is  made  with  a  full  appreciation  of  the  fact  that  profes- 
sional biologists  may  think  that  others  should  be  included. 

It  is  important  to  distinguish  between  the  two  methods 
of  attacking  the  problem.  The  earlier  method,  and  the 


8  Heredity  and  Eugenics 

one  that  prevailed  for  nearly  one  hundred  years,  was  obser- 
vational. Series  of  intergrading  plants  and  animals  were 
observed,  and  by  comparing  them  it  was  inferred  that  they 
represented  the  series  of  transformations  that  had  occurred 
actually  in  nature.  This  has  remained  the  only  possible 
method  for  the  paleontologist,  and  he  also  has  the  advantage 
of  dealing  with  series  of  enormous  length.  It  is  to  be 
expected,  therefore,  that  the  paleontologist  will  be  impressed 
most  strongly  by  those  explanations  of  evolution  which 
have  been  derived  from  observation  and  comparison. 

The  later  method  of  attacking  the  problem,  a  method 
that  has  developed  with  great  rapidity  during  the  last 
decade,  is  experimental.  Plants  and  animals  are  taken  in 
hand  and  are  made  to  show  their  possibilities. 

It  should  be  kept  in  mind  that  the  problem  is  to  explain 
how  one  species  can  produce  another.  The  study  of  organic 
evolution  deals  only  with  the  succession  of  forms,  with  the 
production  of  new  forms  by  previously  existing  ones.  It 
has  nothing  to  say  concerning  origins.  How  the  numerous 
series  of  living  forms  may  have  originated  is  certainly 
beyond  the  reach  of  biological  science  as  yet.  When  one 
goes  beyond  the  observed  changes,  and  tries  to  trace  the 
successions  back  to  their  source,  he  is  in  a  region  of  specu- 
lation, and  outside  the  boundaries  of  science.  One  may 
stand  beside  a  great  stream  and  discover  that  its  waters 
are  moving;  he  also  recognizes  the  direction  of  the  move- 
ment; but  he  can  know  nothing  of  the  distant  sources 
of  the  stream,  for  he  sees  only  a  very  small  section.  So 
the  scientific  recognition  of  organic  evolution  simply 
observes  the  movement  and  its  direction.  The  sources  are 
far  too  distant  for  observation,  and  the  possibilities  are 
too  numerous  for  profitable  speculation.  It  is  evident  that 


Recent  Developments  in  Heredity  and  Evolution  g 

people  in  general  are  more  interested  in  speculation  than 
in  plain  facts ;  and  they  are  so  interested  in  such  speculations 
as  the  origin  of  life  and  the  origin  of  man  that  they  come 
to  believe  that  these  speculations  belong  to  the  scientific 
study  of  organic  evolution.  But  we  are  simply  collecting 
the  facts  of  change  and  trying  to  discover  the  causes  and 
processes  of  change  in  the  plants  and  animals  that  can  come 
under  our  observation.  We  can  thus  discover  laws  of 
evolution,  just  as  we  discover  the  law  of  gravitation,  by 
observing  them  in  operation.  Of  course  the  ultimate 
questions  continually  suggest  themselves,  but  it  must  not 
be  thought  that  any  proposed  answers  to  them  are  a  part 
of  biological  science. 

i.  Environment. — The  first  attempt  at  what  might  be 
called  a  scientific  explanation  of  organic  evolution,  because 
based  upon  observation,  was  that  it  is  caused  by  changes  in 
environment.  This  explanation  began  to  take  definite  form 
during  the  last  decade  of  the  eighteenth  century,  in  the 
writings  of  such  observers  as  Erasmus  Darwin  of  England, 
St.  Hilaire  of  France,  and  Goethe  of  Germany.  Environ- 
ment is  a  term  quite  variable  in  its  biological  application, 
but  we  do  not  need  to  discuss  it  in  this  connection.  These 
older  observers  saw  changes  occurring  in  plants  and  animals 
(especially  the  latter),  in  response  to  changes  in  seasons, 
in  exposure,  in  climate,  etc. ;  and  their  picture  of  the  process 
of  evolution  was  that  plants  and  animals  are  plastic  organ- 
isms that  are  being  molded  by  their  environment.  The 
environment  and  the  molding  were  not  analyzed,  but 
thought  of  in  a  very  superficial  sense;  so  that  it  was  not 
long  before  it  was  recognized  that  the  changes  thus  induced 
are  too  superficial  and  ephemeral  to  furnish  an  adequate 
explanation  of  evolution.  But  it  must  not  be  forgotten 


10  Heredity  and  Eugenics 

that  environment,  even  in  its  superficial  sense,  is  a  very 
real  factor,  and  has  played  its  part  in  every  evolutionary 
theory  since. 

2.  Use  and  disuse. — In  the  early  part  of  the  nineteenth 
century,  the  first  substantial  explanation  of  organic  evolu- 
tion was  proposed.  Its  author  was  Lamarck,  and  the  theory 
has  become  styled  Lamarckism  or  Lamarckianism,  but  its 
author  called  it  "appetency,"  or  the  doctrine  of  desires. 
It  is  more  intelligible  to  the  uninformed  as  the  effect  of  use 
and  disuse.  This  explanation  has  been  a  conspicuous  part 
of  evolutionary  doctrine  ever  since,  and  in  modified  form  is 
known  today  as  neo-Lamarckianism.  The  conception  is 
simple  enough  and  has  a  basis  of  facts.  It  is  well  known, 
for  example,  that  use  develops  a  muscle,  and  that  disuse 
deteriorates  it,  a  deterioration  that  may  reach  as  far  as 
inability  to  function.  If  this  effect  of  use  and  disuse  be 
applicable  to  all  organs  and  regions  of  the  body,  and  certain 
conditions  of  living  were  to  change,  demanding  the  use  of 
structures  that  had  not  been  called  upon  to  do  so  much 
service  before,  and  also  excusing  from  such  constant  service 
structures  that  had  been  very  active  before,  one  might 
imagine  changes  taking  place  in  the  greater  development  of 
certain  structures  and  the  less  development  of  others.  In 
other  words,  change  in  the  environment  means  change  in  the 
demands  on  the  structures  of  plants  and  animals,  and  these 
demands  are  met  by  the  active  exertion  of  the  organism. 

A  well-known  illustration  used  by  Lamarck  will  serve 
our  purpose.  A  grazing  animal,  with  an  ordinary  neck, 
is  placed  in  conditions  that  demand  feeding  upon  the  foliage 
of  trees.  The  continuous  use  of  the  neck  in  stretching 
would  cause  it  to  increase  somewhat  in  length.  This 
slight  increase  in  length  would  be  transmitted  to  the  next 


Recent  Developments  in  Heredity  and  Evolution  n 

generation,  which  in  turn  would  add  to  it,  until  a  number 
of  generations  would  succeed  in  developing  the  exaggerated 
neck  of  the  giraffe. 

This  illustration  makes  clear  the  factors  relied  upon  by 
Lamarck,  namely,  the  effect  of  use  demanded  by  changed 
conditions,  and  the  transmission  of  the  changes  from  parent 
to  offspring.  His  own  name,  "appetency,"  sought  to  ex- 
press the  idea  of  striving  to  satisfy  a  desire;  but,  as  might 
have  been  expected,  it  was  not  understood  by  most  of  the 
people  of  his  day,  and  lent  itself  admirably  to  all  sorts  of 
caricature. 

The  changes  in  structure  brought  about  during  the  life 
of  an  individual  are  spoken  of  as  "acquired  characters," 
and  Lamarck's  explanation  of  the  evolutionary  process 
would  be  impossible  if  acquired  characters  are  not  trans- 
mitted from  parent  to  offspring.  The  present  consensus  of 
opinion  seems  to  be  that  such  acquired  characters  as 
Lamarck  had  in  mind  are  not  transmissible;  but  the  whole 
subject  of  the  transmission  of  acquired  characters  is  more 
a  matter  of  definition  than  anything  else. 

3.  Natural  selection. — It  was  the  explanation  offered  by 
Charles  Darwin,  however,  that  proved  to  be  the  most 
epoch-making  theory  in  the  history  of  biological  science. 
He  called  it  "natural  selection,"  and  it  has  been  a  domi- 
nating conception  for  fifty  years.  With  the  Darwin 
centennial  celebrations  only  two  years  old,  and  with  the 
flood  of  literature  that  accompanied  and  followed  them, 
no  one  interested  in  the  subject  of  evolution  can  be  ignorant 
of  the  meaning  of  natural  selection,  or  of  the  revolution  in 
thought  and  method  brought  about  by  its  presentation  in 
Darwin's  Origin  of  Species.  While  Lamarck's  conception 
was  based  upon  extensive  observation,  and  therefore  was 


12  Heredity  and  Eugenics 

reached  in  a  thoroughly  scientific  way,  Darwin 's  conception 
was  based  upon  an  amount  and  range  of  observation  hitherto 
unapproached;  so  that  if  Lamarck's  approach  was  scien- 
tific, Darwin's  was  still  more  scientific.  In  fact,  Darwin's 
announcement  came  at  a  psychological  moment,  which 
enormously  reinforced  his  message;  and  this  is  not  detract- 
ing in  the  least  from  the  power  and  beauty  of  its  presenta- 
tion. Whether  Darwin's  explanation  stands  or  falls,  his 
supreme  contribution  must  be  regarded  as  the  introduction 
of  a  point  of  view  and  a  method  of  attack  that  not  only 
ushered  in  modern  biology,  but  also  revolutionized  thought 
in  general. 

Natural  selection  is  too  familiar  to  need  extended  expla- 
nation. The  ratio  of  increase  of  organisms,  leading  to 
over-production  and  a  struggle  for  existence,  resulting  in 
the  survival  of  the  fittest,  is  a  series  of  exceedingly  familiar 
phrases,  not  all  of  which  should  be  attributed  to  Darwin. 
That  plants  and  animals  can  be  led  along  in  any  desired 
direction  was  proved  by  experimental  evidence  obtained 
from  the  operations  of  plant  and  animal  breeders ;  and  since 
this  guidance  of  plants  and  animals  by  man  was  by  means 
of  selection,  it  was  most  appropriate  to  call  the  guidance 
by  nature  "natural  selection." 

The  most  significant  fact  connected  with  this  theory 
remains  to  be  mentioned,  and  that  is  the  fact  of  variation. 
Nothing  is  more  clear  than  that  any  machinery  of  evolution 
must  depend  upon  this  fact.  Darwin  greatly  enlarged  the 
horizon  of  our  knowledge  in  reference  to  variation.  It  is 
variation  that  gives  rise  to  individuality  among  plants  and 
animals,  so  that  no  two  plants  or  animals  are  exactly  alike. 
We  have  accustomed  ourselves  to  individuality  among 
human  beings,  for  we  have  been  trained  to  note  the  dis- 


Recent  Developments  in  Heredity  and  Evolution          13 

tinguishing  marks.  But  this  same  individuality  is  no  less 
true  for  all  animals  and  plants.  In  heredity,  therefore, 
there  is  transmitted  not  only  a  likeness  to  the  parent,  but 
also  an  unlikeness,  and  this  unlikeness  constitutes  indi- 
viduality, a  certain  amount  of  variation  from  the  parent. 

Darwin's  conception  was  that  nature  selects  from 
among  these  varying  individuals;  that  the  means  of  selec- 
tion is  the  competition  that  results  from  over-production; 
that  the  better  adapted  individuals  would  naturally  be 
selected  for  survival;  that  their  better  adaptations,  which 
mean  their  individual  peculiarities,  would  be  transmitted 
to  their  offspring;  and  that  such  selection,  continued  genera- 
tion after  generation,  would  so  emphasize  and  increase  the 
favored  variations  that  the  old  species  boundary  would  be 
crossed  and  a  new  species  established.  In  other  words, 
small  variations  would  be  built  up  into  larger  ones,  and 
presently  they  would  become  too  large  to  be  included  within 
the  boundary  of  the  old  species. 

Of  course,  objections  have  been  raised  to  the  theory  of 
natural  selection  as  an  adequate  explanation  of  the  origin 
of  species.  There  can  be  no  doubt  but  that  there  is  selec- 
tion in  nature,  in  the  sense  that  not  all  the  forms  produced 
survive;  but  many  believe  that  this  cannot  change  forms 
enough  to  be  regarded  as  new  species;  that  any  selection 
thus  made  cannot  be  on  the  basis  of  any  "  life-and-death " 
advantage  of  structure  that  one  individual  has  over  another; 
and  that  the  variations  thus  used  are  only  the  so-called 
"fluctuating  variations"  which  have  nothing  definite  in 
them  as  to  direction  or  amount. 

4.  Mutation. — We  come  now  to  the  work  of  the  last 
decade,  which  is  characterized  by  the  rapid  development 
of  the  study  of  evolution  by  using  experimental  methods. 


14  Heredity  and  Eugenics 

Perhaps  the  most  influential  work  to  enforce  the  experi- 
mental method  was  that  of  DeVries,  in  developing  his 
theory  of  mutation.  His  great  contribution,  therefore, 
must  not  be  regarded  as  offering  mutation  as  an  explana- 
tion of  the  origin  of  species,  for  that  explanation  may  not 
stand,  but  as  establishing,  or  at  least  powerfully  helping  to 
establish,  the  study  of  evolution  upon  an  experimental  basis. 

The  mutation  theory  needs  no  extended  explanation, 
for  the  current  literature  of  organic  evolution  is  full  of  it. 
The  long  series  of  cultures  of  Oenothera,  under  rigid  control 
and  in  large  numbers,  are  familiar.  The  appearance,  in 
relatively  very  small  numbers,  of  widely  different  indi- 
viduals, which  "came  true"  in  subsequent  generations,  led 
to  the  inference  that  new  species  were  appearing  under 
observation,  suddenly  produced  by  the  parent  form,  fully 
equipped  as  species,  without  any  intermediate  stages  or 
any  building  up  by  selection.  It  should  be  noted  that  this 
does  not  banish  natural  selection  as  a  factor  in  evolution, 
but  assigns  to  it  a  new  role,  which  is  not  to  produce  species, 
but  to  select  among  those  already  produced. 

The  study  of  mutations  is  one  of  the  vigorous  phases  of 
experimental  work  today,  and  some  of  the  results  will  be 
presented  in  the  subsequent  chapters.  Objections  to  the 
theory  have  developed,  as  must  be  the  case  in  all  theories. 
There  are  questions  as  to  the  extent  of  mutation  as  a  process 
going  on  among  plants  and  animals;  as  to  its  reliability  in 
producing  species;  as  to  whether  mutants  are  really  new 
forms,  or  only  old  ones  derived  from  a  splitting  hybrid 
parent.  It  is  such  questions,  and  others  like  them,  that 
experimental  work  today  is  trying  to  answer. 

5.  Orthogenesis. — The  barest  kind  of  evolutionary  back- 
ground would  be  inadequate  without  a  mention  of  ortho- 


Recent  Developments  in  Heredity  and  Evolution  15 

genesis.  The  variations  utilized  in  the  preceding  explana- 
tions, both  the  smaller  ones  used  by  natural  selection  and 
the  larger  ones  used  by  mutation,  occur  in  every  direction 
from  the  parent  form,  the  successful  direction  being  deter- 
mined by  natural  selection.  This  has  been  called  indeter- 
minate variation.  In  tracing  the  evolution  of  great  groups, 
however,  it  becomes  clear  that  the  most  important  varia- 
tions occur  in  certain  definite  directions,  which  have  been 
maintained  persistently  throughout  all  possible  changes  of 
condition.  For  example,  the  history  of  such  a  group  as 
gymnosperms  shows  a  tendency  to  vary  in  certain  definite 
directions  that  has  persisted  from  the  early  Paleozoic  to 
the  present  time.  In  other  words,  there  is  much  to  indicate 
that  while  variation  may  be  indeterminate,  there  are  also 
certain  definite  lines  that  persist.  The  origin  of  new  forms, 
whether  by  natural  selection  or  mutation  or  neither,  as  the 
result  of  a  persistent  determinate  variation,  is  called  ortho- 
genesis. It  certainly  removes  one  of  the  greatest  difficul- 
ties in  the  way  of  natural  selection,  and  that  is  the  beginning 
and  development  of  a  structure  that  can  be  of  advantage 
only  when  it  is  completed.  It  satisfies  also  the  many 
known  cases  of  excessive  development  in  certain  directions, 
a  development  that  may  be  not  only  disadvantageous,  but 
even  destructive.  Even  if  determinate  variation  is  accepted 
as  a  fact,  however,  what  determines  the  persistent  variation  ? 
The  answer  to  this  question  has  resulted  in  many  variations 
of  the  theory  of  orthogenesis. 

It  should  be  noted  that  natural  selection,  mutation,  and 
orthogenesis  are  not  mutually  destructive.  They  all  deal 
with  variations,  and  may  all  be  operative  in  producing  new 
forms.  Natural  selection  deals  with  small  variations  which 
are  in  every  direction ;  mutation  with  large  variations  which 


1 6  Heredity  and  Eugenics 

are  in  every  direction;  and  orthogenesis  with  those  small 
or  large  and  relatively  few  variations  which  for  some  reason 
persist  and  increase  from  generation  to  generation  and  carry 
forward  the  group  as  a  whole. 

4.      BIOMETRY 

When  the  idea  of  natural  selection  became  dominant, 
and  new  species  were  believed  to  have  arisen  by  the  accumu- 
lation of  small  variations,  which  seemed  to  be  indefinite 
and  fluctuating,  a  statistical  method  of  attack  began  to  be 
developed,  a  method  that  has  been  named  biometry.  The 
most  conspicuous  names  that  one  meets  in  the  literature  of 
biometry  are  Galton,  the  English  pioneer  in  the  exploitation 
of  the  method;  and  Pearson,  who  has  been  largely  instru- 
mental in  carrying  it  forward  into  its  more  advanced 
mathematical  stage. 

It  is  a  method  that  deals  with  groups  or  populations, 
rather  than  with  individuals,  and  its  results  present  the 
averages  of  variations.  It  is  evident  that  an  average 
obtained  from  the  measurements  of  a  given  character  in  a 
series  of  individuals  will  depend  upon  the  individuals 
selected  for  measurement.  Therefore,  biometry  demands 
to  an  unusual  degree  the  elimination  of  preconceived  opin- 
ions and  the  exercise  of  great  judgment.  It  has  become 
so  special  and  intricate  a  method  that  it  can  be  followed, 
with  full  understanding,  only  by  those  with  special  training; 
so  that  any  adequate  illustration  of  it  will  be  left  to  such  of 
the  subsequent  addresses  as  may  have  occasion  to  apply  it. 

A  word  can  be  said,  however,  concerning  its  use  as  an 
instrument  in  the  study  of  the  processes  of  evolution. 
Selecting  any  character  or  group  of  characters  that  are  to 
be  measured  or  counted,  and  using  a  wisely  selected  range  of 


Recent  Developments  in  Heredity  and  Evolution          17 

material,  biometry  reveals  the  prevailing  tendency,  in 
reference  to  these  variations,  in  a  group  of  individuals 
representing  a  species,  a  tendency  that  could  not  be  recog- 
nized by  the  study  of  a  single  individual.  Applying  this 
method  to  successive  generations  from  this  group  of  indi- 
viduals, under  experimental  control,  it  can  be  discovered 
whether  the  prevailing  tendency  in  the  expression  of  these 
variations  remains  the  same,  continuing  the  species  as 
before;  or  shifts,  modifying  the  species  as  a  whole;  or 
splits  up,  giving  rise  to  a  second  marked  tendency,  that 
may  mean  presently  two  distinct  species. 

It  is  evident  that  such  data  can  be  very  suggestive,  but 
that  their  limitations  must  be  recognized.  They  are  data 
concerning  successive  populations,  and  show  the  average 
result  of  individual  variation  as  expressed  in  a  population. 
In  other  words,  they  present  in  concrete  and  somewhat 
definite  form  the  problems  of  variation  and  inheritance 
that  must  be  solved. 

5.      HEREDITY 

It  must  have  become  evident,  during  the  preceding 
sketch  of  representative  theories  of  evolution,  that  the 
fundamental  factor  in  the  process  is  variation,  and  that  the 
essential  and  inevitable  question  behind  all  of  these  explana- 
tions is  the  origin  of  variation.  This  brings  us  at  once  to 
the  problem  of  heredity,  with  its  supposed  processes  for 
transmitting  what  we  call  "characters"  from  parent  to 
offspring.  How  is  variation  secured  in  this  transmission? 
The  earlier  observers  simply  accepted  variation  as  a  fact, 
and  made  no  serious  attempt  to  explain  it. 

The  first  attack  upon  this  problem  was  the  accumulation 
of  data  in  reference  to  the  facts  of  heredity.  To  accumulate 


1 8  Heredity  and  Eugenics 

these  facts  in  such  numbers  as  to  make  any  generaliza- 
tion worthy,  demands  the  culture  through  many  generations, 
under  most  rigid  control,  of  the  largest  possible  number  of 
plants  and  animals.  This  means  long  periods  of  time,  great 
patience,  and  many  investigators.  The  number  of  investi- 
gators is  multiplying,  the  range  of  material  is  increasing, 
and  the  period  covered  by  some  of  the  work  has  now  been 
sufficient  to  justify  some  presentation  of  the  results. 

Probably  the  most  conspicuous  working  hypothesis 
today,  in  connection  with  the  collection  and  interpreta- 
tion of  the  data  of  heredity,  is  the  one  called  "Mendel's 
law."  This  is  to  be  made  a  special  theme  in  the  course  of 
this  series,  but  a  brief  statement  in  reference  to  it  will 
help  the  background  and  may  prepare  the  way  for  the  later 
discussion.  This  Austrian  monk,  who  worked  in  his 
monastery  garden  during  the  middle  of  the  last  century, 
left  on  record  what  is  called  a  law  of  heredity.  This  record 
was  lost,  so  far  as  its  influence  was  concerned,  until 
ten  or  fifteen  years  ago,  when  the  modern  movement  in 
experimental  evolution  began  to  be  vigorous.  Now  the 
Mendelians  constitute  a  conspicuous  biological  cult,  and 
Mendelism  has  extended  from  its  simple  original  state- 
ment into  a  speculative  philosophy,  with  conceptions  of 
unit-characters,  dominance,  ratios,  etc.,  that  the  untrained 
cannot  follow. 

The  fundamental  conception  is  simple  enough.  If  two 
different  species  are  crossed,  the  result  is  a  hybrid  which 
combines  certain  characters  of  both  parents.  When  this 
hybrid  propagates,  the  progeny  splits  up  into  three  sets: 
one  set  resembling  the  hybrid  parent;  and  the  two  other 
sets  resembling  the  parent  forms  that  entered  into  the 
hybrid.  Mendel's  law  is  a  statement  of  the  definite  ratio 


Recent  Developments  in  Heredity  and  Evolution  19 

expressed  by  these  three  groups  of  forms  derived  from  a 
splitting  hybrid.  This  means  that  in  a  series  of  genera- 
tions initiated  by  a  hybrid,  approximately  one-half  of  the 
individuals  of  each  generation  will  represent  the  hybrid 
mixture,  one-fourth  of  the  individuals  will  represent  one 
of  the  pure  forms  that  entered  into  the  hybrid,  and  the 
remaining  fourth  will  represent  the  other  pure  form. 

It  should  be  understood  that  the  use  of  hybrids  in  such 
experimental  work  is  simply  a  device  to  secure  easy  recog- 
nition of  the  contributions  of  each  parent  to  the  progeny. 
For  example,  if  red  and  yellow  races  of  corn  are  crossed,  it 
is  very  simple  to  recognize  the  color  contribution  of  each 
parent  to  the  hybrid  progeny,  when  it  would  be  impossible 
to  separate  the  contribution  of  two  yellow  parents.  The 
inference  is,  that  what  is  true  of  hybrids  is  true  of  forms 
produced  in  the  ordinary  way,  so  that  laws  of  heredity 
obtained  from  a  study  of  hybrids  may  be  regarded  as 
laws  of  heredity  in  general.  In  one  sense,  every  union  of 
parent  forms  is  hybridizing,  for  each  parent  has  its  own 
individuality. 

One  of  the  more  subtle  problems  that  has  arisen  in 
connection  with  such  investigations  is  the  problem  of  sex 
determination.  In  all  organisms  with  sex  differentiation, 
progeny  is  produced  by  the  fusion  of  male  and  female 
sexual  cells,  and  this  progeny  develops  as  distinct  male 
and  female  individuals.  It  is  one  thing  to  determine  the 
general  structure  of  an  organism  by  some  law  of  heredity, 
but  a  very  different  thing  to  determine  why  any  individual 
thus  produced  is  sometimes  male  and  sometimes  female. 

The  work  of  today  is  not  resting  content  with  the  patient 
collection  of  the  facts  of  heredity,  with  determining  ratios 
as  expressions  of  laws,  and  with  the  end  results  of  processes 


20  Heredity  and  Eugenics 

initiated  under  experimental  control.  There  is  keen  search- 
ing for  cytological  evidence;  and  the  structure  and  behavior 
of  the  sexual  cells,  through  the  whole  process  of  their  forma- 
tion, during  the  act  of  fusion,  and  in  the  initiating  activity 
of  the  fertilized  egg,  are  being  subjected  to  all  the  scrutiny 
that  a  developing  technique  can  devise  to  discover  the 
mechanism  of  heredity.  Moreover,  cytological  evidence  is 
being  searched  for  not  only  to  discover  a  possible  physical 
basis  for  heredity,  which  would  mean  actual  material 
machinery,  but  also  to  discover  the  possible  relations  of 
chemical  and  physical  factors  to  this  most  fundamental 
and  obscure  process.  It  is  believed  that  it  must  be  a 
response,  in  terms  of  chemistry  and  physics,  by  a  living 
material  substance. 

6.     PRACTICAL  APPLICATIONS 

In  a  university  atmosphere,  the  chief  interest  is  probably 
focused  upon  the  attempt  to  reveal  one  of  the  so-called 
"mysteries"  of  life,  those  mysteries  which  always  invite 
one  to  uncover  them;  but  there  is  another  aspect  of  these 
problems  worth  considering.  The  experimental  work  that  has 
been  done  in  the  study  of  heredity  and  evolution  has  had  a 
very  important  bearing  upon  the  practical  handling  of  plants 
and  animals,  including  the  human  animal.  The  applica- 
tions have  been  made  to  plants  most  extensively,  and 
methods  of  plant  breeding  have  been  revolutionized.  The 
recognition  that  commercially  "pure  seed"  is  an  extensive 
mixture  of  different  types  or  strains,  has  led  to  their 
separation,  and  has  changed  the  clumsy  and  inefficient 
method  of  mass  culture  to  the  definite  and  exact  method  of 
pedigree  culture.  As  a  consequence,  the  number  of  forms 
made  available  for  culture  has  been  multiplied  enormously, 


Recent  Developments  in  Heredity  and  Evolution  21 

having  simply  been  discovered  and  pedigreed,  without  the 
labor  of  continuous  selection  year  after  year,  and  without 
the  old  inconstancy  in  the  result.  To  reduce  labor,  to 
multiply  cultural  forms,  and  to  obtain  constant  results 
in  plant  breeding  are  results  of  very  large  importance  to 
the  material  side  of  human  welfare.  Pedigree  culture  has 
not  only  multiplied  available  forms,  but  it  has  begun  to 
be  used  most  effectively  in  combating  drought  and  disease, 
the  most  dangerous  enemies  of  cultivated  plants.  Drought- 
resistant  races  are  being  developed  from  pedigreed  stock, 
and  immunity  to  different  diseases  has  been  found  to  be 
a  transmissible  character.  When  it  is  remembered  that 
drought-resistance  not  only  insures  crops  over  areas  now 
cultivated,  but  also  secures  an  enormous  extension  of  area 
that  can  be  cultivated;  and  that  the  annual  losses  from 
plant  diseases  represent  an  enormous  financial  total;  it 
will  be  appreciated  that  the  study  of  heredity  and  evolution, 
with  purely  scientific  purpose,  incidentally  has  been  enor- 
mously profitable  on  the  practical  side. 

I  have  sketched  a  background  that  will  permit  those  who 
follow  to  put  their  work  in  its  setting  without  much  loss 
of  time.  The  interest  lies  chiefly  in  the  foreground  that 
they  will  develop,  for  it  will  represent  the  work  of  today. 


CHAPTER  II 

THE  PHYSICAL  BASIS  OF  HEREDITY  AND  EVOLUTION 
FROM  THE  CYTOLOGICAL  STANDPOINT 

Heredity  involves  not  only  the  transmission  of  similarity 
in  structure,  but  also  the  transmission  of  dissimilarity. 
Likeness  means  close  relation  to  the  parent  forms;  unlike- 
ness  means  individuality.  It  is  not  generally  appreciated 
that  individuality  expresses  itself  just  as  certainly  among 
plants  and  animals  as  among  human  beings.  We  have 
learned  to  recognize  the  marks  of  individuality  among 
human  beings  through  long  acquaintance,  but  we  should 
realize  also  that  no  two  plants  or  animals  are  exactly  alike. 
It  is  this  individuality  that  is  called  variation,  and  variation 
is  the  basis  of  evolution.  The  phenomena  of  heredity 
established  as  facts  by  series  of  cultures  under  rigid  control, 
however,  must  be  recognized  as  the  end  results,  between 
which  and  the  act  of  fertilization  there  extends  a  series  of 
unknown  processes,  with  which  as  yet  only  scientific  imagi- 
nation deals. 

The  purpose  of  this  chapter  is  to  inquire  whether  there 
is  any  physical  basis  for  the  transmission  of  like  and  unlike 
characters,  in  the  same  sense  that  protoplasm  was  long  ago 
called  "the  physical  basis  of  life."  This  phrase  only  means 
that  protoplasm  is  the  material  substance  in  which  the 
phenomena  of  life  are  manifested.  Is  there  any  substance 
or  structure  by  means  of  which  the  phenomena  of  heredity 
manifest  themselves  ? 

The  answer  to  this  question  would  be  given  more  appro- 
priately by  some  biologist  who  has  made  it  the  special 


Physical  Basis  of  Heredity  and  Evolution  23 

subject  of  his  investigations.  This  chapter,  therefore, 
must  be  regarded  simply  as  the  presentation  of  a  teacher, 
to  explain  a  subject  that  belongs  logically  in  the  series. 
Another  restriction  is  that  this  presentation  deals  chiefly 
with  structures  that  are  visible  by  means  of  laboratory 
technique,  and  not  with  the  results  of  experiment  upon 
these  structures.  A  final  restriction  is  that  the  statements 
deal  with  plants,  a  limitation  necessary  to  the  writer,  and 
offset  by  the  fact  that  the  corresponding  facts  hi  animals 
will  be  stated  in  one  of  the  later  chapters. 

Some  conception  of  what  is  meant  by  the  power  of  repro- 
duction will  be  useful.  Among  the  simplest  plants,  every 
cell  has  this  power;  hi  fact,  some  plants  are  so  simple  that 
the  adult  body  consists  of  a  single  cell.  As  plant  bodies 
came  to  be  made  up  of  numerous  cells,  some  of  them  lost 
the  power  of  reproduction;  and  as  the  body  became  increas- 
ingly complex,  the  number  of  cells  retaining  the  power  of 
reproduction  became  relatively  smaller.  This  means  that 
in  the  complex  plant  body,  the  relatively  few  reproductive 
cells  are  not  so  much  "cells  set  apart  for  this  special  func- 
tion," as  cells  that  have  not  lost  this  primary  power.  The 
specialized  cells  are  not  those  that  reproduce,  but  those 
that  cannot.  The  loss  of  reproductive  power  is  usually 
not  complete,  for  most  cells  can  reproduce  their  own  kind, 
even  if  they  cannot  reproduce  the  whole  body. 

This  leads  to  a  consideration  of  what  is  included  in  full 
reproductive  power.  Without  including  confusing  details, 
it  may  be  said  that  such  reproduction  as  one  has  in  mind 
in  connection  with  heredity  involves  four  general  things. 
First,  there  is  cell  multiplication,  the  fertilized  egg  initiating 
a  series  of  cell  divisions  that  may  result  in  a  multitude  of 
cells.  It  is  evident,  however,  that  a  complex  plant  body  is 


24  Heredity  and  Eugenics 

more  than  a  multitude  of  similar  cells.  In  the  second  place, 
there  is  cell  differentiation,  groups  of  cells  becoming  different, 
so  that  the  various  tissues,  with  their  special  functions,  are 
developed.  In  the  third  place,  tissues  must  be  organized 
together  into  the  structures  called  organs.  In  the  last 
place,  the  organs  must  be  combined  in  making  that  total 
organization  called  the  individual.  It  is  this  far-reaching 
directive  influence  that  is  the  most  baffling  fact  in  connection 
with  heredity. 

To  obtain  any  impression  of  the  supposed  machinery  of 
heredity,  it  is  necessary  to  know  something  of  the  structure 
of  a  living  cell.  So  far  as  material  goes,  such  a  cell  is  an 
individualized  mass  of  protoplasm.  This  protoplasm  is 
organized  into  a  body  known  conveniently  as  the  proto- 
plast, which  is  the  living  body  of  the  cell.  In  plants,  the 
protoplast  usually  constructs  a  cellulose  wall  about  itself, 
which  has  given  rise  to  the  impression  that  a  cell  is  a  walled 
chamber  containing  protoplasm.  In  the  plant  cells  which 
have  to  do  directly  with  heredity,  however,  namely  the 
reproductive  cells,  the  cellulose  wall  is  not  formed,  and 
they  are  naked  protoplasts.  The  protoplast  is  exceedingly 
complex,  as  cytologists  well  know,  and  includes  a  variety 
of  organs.  Conspicuous  among  these  protoplasmic  organs  is 
the  nucleus,  which  is  a  more  or  less  spherical  body  and  usually 
sharply  limited  from  the  rest  of  the  protoplast,  in  which  it 
lies  imbedded  (Fig.  i).  The  remainder  of  the  protoplasmic 
material  enters  into  the  structure  of  the  cytoplasm,  another 
organ  or  region  of  the  protoplast  constantly  associated 
with  the  nucleus.  Every  living  cell  contains  a  nucleus  and 
cytoplasm,  and  in  addition  there  may  be  other  protoplasmic 
organs  (Fig.  i),  but  the  two  mentioned  are  those  that  belong 
to  this  discussion. 


Physical  Basis  of  Heredity  and  Evolution 


As  in  the  case  of  all  organs,  the  cytoplasm  and  the  nucleus 
are  associated  with  special  functions.  This  does  not  mean 
that  each  does  a  certain  thing  and  nothing  else,  but  that  each 
is  conspicuous  in  connection  with  a  certain  kind  of  work. 
Especially  unsafe  is  it  to 
ascribe  certain  definite 
functions  to  these  organs  of 
the  protoplast,  because  pro- 
toplasm itself  is  so  little 
understood.  In  any  event, 
the  cytoplasm  seems  to  be 
conspicuously  associated 
with  the  metabolic  activi- 
ties of  the  cell;  and  it  is 
certain  that  the  nucleus  is 
conspicuously  associated 
with  cell  division.  When 
division  occurs,  and  one 
cell  gives  rise  to  two  cells, 
this  process  almost  invari- 
ably begins  with  the  nu- 
cleus, which  may  thus  be 
said  to  initiate  cell  division. 
It  must  be  understood 
clearly  that  we  are  speak- 
ing of  visible  changes  hi 
structure,  behind  which  and 
accompanying  which  there  are  certainly  numerous  invisible 
physical  and  chemical  changes. 

It  is  evident  that  the  problem  of  heredity  is  involved 
in  the  process  of  cell  division,  for  through  this  process  the 
old  cell  transmits  whatever  determines  the  characters  of 


FIG.  i. — Cells  from  a  moss  leaf:  each 
of  the  complete  cells  shows  the  well- 
defined  nucleus;  since  the  leaf  is  green, 
there  are  also  numerous  green  protoplas- 
mic organs  (chloroplasts) ;  the  remaining 
granular-looking  ground  substance  is  the 
cytoplasm. 


26  Heredity  and  Eugenics 

the  two  new  cells.  In  ordinary  cell  division,  the  imme- 
diate transmission  seems  to  be  a  similar  structure,  for  the 
new  cells  resemble  the  old  one  in  all  recognizable  features. 
In  the  differentiation  of  cells,  however,  certain  cell  divisions 
involve  the  transmission  of  unlike  characters. 

This  relation  of  the  nucleus  to  cell  division,  and  of  cell 
division  to  heredity,  has  focused  the  attention  of  cytolo- 
gists  upon  the  structure  and  behavior  of  the  nucleus.  No 
structure  of  plants  and  animals  has  received  such  detailed 
and  persistent  investigation  as  has  the  nucleus,  and  much 
of  the  advance  in  technique  associated  with  the  use  of  the 
microscope  has  been  stimulated  by  the  necessity  of  learning 
more  about  the  nucleus. 

If  the  nucleus  is  the  conspicuous  structure  associated 
with  cell  division,  the  suggestion  is  natural  that  it  is  the 
material  structure  associated  with  heredity.  But  the 
nucleus  is  a  complex,  and  most  conspicuous  in  its  structure 
is  a  substance  called  chromatin.  In  the  ordinary  nucleus 
it  appears  as  a  network  of  denser  material,  which  has 
received  its  name  from  the  fact  that  it  takes  stains  easily, 
being  the  most  stainable  substance  in  the  nucleus  (Fig. 
2,  a).  If  there  is  any  definite  material  that  deserves  to  be 
called  the  physical  basis  of  heredity,  it  is  probably  chro- 
matin, which  of  course  is  a  protoplasmic  substance.  This 
belief  is  largely  based  upon  the  behavior  of  chromatin 
during  cell  division. 

In  preparation  for  division,  the  chromatin  network 
becomes  an  evident  continuous  band,  which  resembles  a. 
tangled  skein  (Fig.  2,  6).  This  band  shortens  and  corre- 
spondingly thickens,  and  finally  breaks  up  into  a  definite 
number  of  units,  called  chromosomes  (Fig.  2,  c).  These 
chromosomes  are  thus  chromatin  individually  organized, 


Physical  Basis  of  Heredity  and  Evolution 


27 


in  the  same  sense  that  protoplasts  are  protoplasm  indi- 
vidually organized,  and  they  are  thought  to  retain  their 
individual  identity  through  all  the  apparent  fusions  into 
bands  and  network.  It  is  the  chromosome,  therefore, 
consisting  of  the  material  chromatin,  that  is  regarded  as  the 
organized  carrier  of  transmissible  characters;  hence  the 
behavior  of  the  chromosomes  in  cell  division  becomes  a 


e  f  g  h 

FIG.  2. — Diagram  of  stages  in  nuclear  division. — After  Lock 

matter  of  first  importance  in  considering  the  machinery  of 
heredity. 

One  of  the  important  facts  to  note  is  the  definite  number 
of  chromosomes.  Each  kind  of  plant  and  animal  has  its 
own  number.  For  example,  in  certain  plants  the  number 
is  6;  in  others  it  may  be  considerably  more  than  100;  and 
of  course  the  intermediate  numbers  are  well  represented. 
Differences  in  the  number  of  chromosomes  may  occur 


28  Heredity  and  Eugenics 

among  very  closely  related  plants,  or  the  number  may  be 
constant  throughout  a  great  group.  For  example,  in  the 
gymnosperms,  so  far  as  known,  the  number  is  almost  con- 
stantly 12.  This  fact  has  given  rise  to  the  suggestion  that 
the  number  of  chromosomes,  as  well  as  their  quality,  may 
be  a  factor  in  heredity,  but  too  much  stress  must  not  be  laid 
upon  it  as  yet. 

While  the  chromosomes  are  becoming  separate,  a  spindle 
of  fibers  is  formed  about  the  nucleus,  and  the  chromosomes 
become  attached  to  the  fibers,  finally  being  arranged  about 
the  equator  of  the  spindle  (Fig.  2,  d).  In  this  position, 
each  chromosome  splits  longitudinally  (Fig.  2,  e),  and  the 
two  halves,  by  the  shortening  of  attached  fibers,  are  drawn 
toward  the  opposite  poles  of  the  spindle  (Fig.  2,  /),  the 
old  chromosome  thus  being  represented  at  each  pole  by  a 
half-chromosome.  The  half -chromosomes  at  each  pole 
enter  into  the  organization  of  a  new  nucleus  (Fig.  2,  g), 
wall  material  is  deposited  in  the  plane  of  the  equator  of  the 
spindle  and,  extending  through  the  cytoplasm,  cuts  the  old 
cell  into  two  new  cells,  each  with  its  nucleus  (Fig.  2,  ti). 
It  is  evident  that  each  new  nucleus  has  the  same  number 
of  chromosomes  as  the  old  one,  and  that  each  chromosome 
of  the  new  nuclei  represents  in  material  a  chromosome  of 
the  parent  nucleus. 

This  detailed  and  precise  process  in  the  behavior  of 
chromosomes,  insuring  the  transmission  from  one  cell  to 
its  progeny  cells  of  the  identical  material  contained  in 
every  chromosome,  is  a  strong  argument  in  favor  of  regard- 
ing the  chromosome  as  the  carrier  of  hereditary  qualities. 

The  kind  of  reproduction  with  which  the  problems  of 
heredity  are  concerned  chiefly,  however,  is  that  which 
involves  the  fusion  of  sexual  cells.  There  are  three  distinct 


Physical  Basis  of  Heredity  and  Evolution 


29 


methods  of  reproduction  recognized  among  plants.  The 
most  primitive  method  is  vegetative  multiplication,  ordinary 
vegetative  cells  producing  new  plants.  In  the  transmission 
of  hereditary  qualities  this  involves 
simply  a  series  of  such  cell  divisions 
as  has  been  described  above. 

Later  in  the  evolution  of  plants, 
the  power  of  reproduction  was  dis- 
played chiefly  by  spores,  which  at 
first  were  only  certain  protoplasts 
that  escaped  from  the  incasing  wall. 
In  most  cases,  before  escape  the 
protoplast  divides,  so  that  there 
issue  from  the  old  cell  two  or  more 
naked  protoplasts  or  spores.  Since 
the  early  spores  belonged  to  water 
plants,  they  had  swimming  append- 
ages (cilia),  and  were  called  swim- 
ming spores  or  zoospores  (Fig.  3,  a 
and  b).  Any  one  of  these  swim- 
ming spores,  under  appropriate 
conditions,  can  produce  a  new  in- 
dividual. This  method  of  multi- 
plying individuals  remains  the  most 
effective  method  among  plants. 

Vegetable  multiplication  and 
reproduction  by  spores  are  both  sexless  methods,  and  it  is 
quite  evident  that  the  introduction  of  the  sexual  method  is 
more  significant  than  merely  a  third  method  of  reproduction. 

It  is  demonstrable  among  plants  that  the  sexual  cells 
(gametes)  were  derived  from  the  swimming  spores  (zoospores). 
In  certain  plants,  if  a  protoplast  divides  and  gives  rise  to 


FIG.  3. — A  portion  of  a  fila- 
ment of  a  green  alga  (Ulothrix) : 
a,  zoospores  in  mother  cell;  b, 
an  escaped  zoospore;  c,  ga- 
metes, most  of  which  have 
escaped  from  the  mother  cell; 

d,  gametes  pairing  and  fusing; 

e,  zygotes. 


30  Heredity  and  Eugenics 

few  and  comparatively  large  protoplasts,  they  are  swim- 
ming spores  (Fig.  3,  &  and  6),  and  each  can  reproduce.  If 
the  divisions  continue,  however,  and  result  in  numerous 
and  comparatively  small  protoplasts,  they  are  unable  to 
reproduce  (Fig.  3,  c).  However,  if  they  come  together  in 
pairs  and  fuse  (Fig.  3,  d),  thus  making  one  cell  (protoplast) 
out  of  two  (Fig.  3,  e),  the  new  cell  can  reproduce.  This 
fusion  is  the  sexual  act,  and  the  fusing  cells  are  the  sexual 
cells  (gametes).  It  is  of  interest  to  note  that  this  first 
appearance  of  sex  is  quite  disconnected  with  the  multipli- 
cation of  individuals.  Individuals  are  multiplied  through- 
out the  growing  season  by  the  spores.  Toward  the  close 
of  the  season,  the  gametes  begin  to  appear,  and  the  fusion 
cells  (zygotes)  formed  by  their  pairing  develop  heavy  walls 
that  protect  them  through  the  unfavorable  season  (as  the 
winter).  All  the  other  structures  of  the  plant  perish,  and 
it  exists  through  the  winter  only  in  the  form  of  zygotes. 
At  the  beginning  of  the  next  season,  the  zygotes  produce 
new  plants,  and  these  are  multiplied  by  spores.  The 
service  rendered  by  the  sex  act  in  this  case,  therefore,  is  to 
produce  a  protected  cell,  which  can  carry  the  plant  through 
an  unfavorable  period;  in  short,  the  service  is  protection 
rather  than  multiplication. 

The  next  advance  in  the  evolution  of  sex  was  its  differ- 
entiation. The  gametes  at  first  are  similar  in  appearance 
and  in  behavior,  but  it  must  be  recognized  that  this  optical 
test  would  be  unable  to  detect  any  differences  in.  quality. 
It  is  upon  the  basis  of  appearance  that  such  gametes  are 
said  to  be  unisexual,  which  only  means  that  they  cannot 
be  distinguished  as  male  and  female.  A  series  can  be 
arranged  to  illustrate  a  gradual  differentiation  of  gametes 
into  two  forms,  unlike  in  appearance  and  in  behavior.  In 


Physical  Basis  of  Heredity  and  Evolution  31 

one  case,  the  gamete  becomes  larger  and  larger,  its  power 
of  movement  diminishing  at  the  same  time,  until  at  last 
it  becomes  a  very  large  and  entirely  passive  cell.  In  the 
other  case,  the  gamete  retains  its  small  size  and  activity. 
These  two  very  dissimilar  gametes  are  the  egg  and  the 
sperm,  easily  distinguishable  female  and  male  cells  (Fig.  4). 
The  essential  difference  thus  brought  about  is  the  great  in- 


FIG.  4. — -A  single  large  egg  and  numerous  small  sperms  of  rockweed  (Fucus) 

crease  in  the  bulk  of  the  gamete  that  becomes  the  egg, 
but  the  constant  feature,  which  is  not  changed,  is  the  chro- 
matin,  the  increase  in  bulk  being  due  to  an  increase  of 
cytoplasm.  This  constancy  of  the  chromatin,  coupled  with 
the  known  fact  that  the  two  gametes  contribute  alike  to 
their  progeny,  indicates  that  the  chromatin  is  the  essential 
material  in  heredity.  Since  both  cytoplasm  and  nuclei  are 
involved  in  the  sexual  fusion,  it  may  be  claimed  that  the 


Heredity  and  Eugenics 


cytoplasm  is  as  essential  to  the  process  as  the  nucleus;  but 
in  certain  plants,  notably  Lilium,  it  has  been  demonstrated 
that  when  fusion  occurs  there  is  no  cytoplasm  whatsoever 
investing  the  male  nucleus.  It  seems  safe  to  conclude, 
therefore,  that  the  nucleus  contains  the  material  essential 
to  the  phenomena  of  heredity;  and  if  so,  chromatin 
must  be  the  material,  and  the  chromosomes  its  visible 
organized  units. 

A  very  simple  case  will  serve  to  illustrate  the  results  of 
the  sexual  fusion  upon  the  chromosome  situation.    Imagine 

the  fusion  of  an  egg  and  a 
sperm,  each  of  whose  nuclei 
contains  two  chromosomes 
(Fig.  5,  i  and  2).  The  nu- 
cleus of  the  fertilized  egg 
would  contain  four  chromo- 
somes (Fig.  5,  3),  two  of 
them  maternal  (contributed 
by  the  egg),  and  two  of 
them  paternal  (contributed 
by  the  sperm).  Suppose 
that  two  of  the  four  domi- 
nate in  determining  the 
structure  of  the  new  indi- 
vidual to  be  developed  from 
the  fertilized  egg.  It  will 
be  seen  that  there  are  four 

possible  pairs:  (i)  the  paternal  pair  (Fig.  5,  4),  in  which 
case  the  new  individuals  would  resemble  the  male  parent; 
(2)  the  maternal  pair  (Fig.  5,  7),  in  which  case  the  resem- 
blance would  be  to  the  female  parent;  (3)  two  pairs  (Fig.  5, 5 
and  6},  each  consisting  of  a  dominant  male  and  a  dominant 


FIG.  5. — Diagram  illustrating  result 
of  sexual  fusion:  i,  sperm  containing  two 
chromosomes  (A A);  2,  egg  containing 
two  chromosomes  (BB) ;  j,  fertilized  egg 
containing  four  chromosomes  (two  pa- 
ternal and  two  maternal) ;  4,  domination 
of  paternal  chromosomes;  5  and  6,  domi- 
nation of  one  paternal  and  one  maternal 
chromosome;  7,  domination  of  maternal 
chromosomes. 


Physical  Basis  of  Heredity  and  Evolution  33 

female  chromosome,  in  which  case  the  new  individual  would 
be  a  mixture,  resembling  both  parents.  Expressing  the 
chances  in  the  form  of  a  ratio,  they  could  be  represented  as 
1:2:1.  This  is  a  simple  expression  of  Mendel's  law,  defined 
in  the  preceding  chapter.  The  formulation  of  Mendel's 
law  was  based  upon  the  observed  facts  of  heredity;  and  this 
chromosome  situation  supplies  for  it  a  cytological  basis. 

It  must  be  understood  clearly  that  so  simple  an  illus- 
tration does  not  represent  the  actual  facts,  for  chromosomes 
are  usually  more  numerous,  and  eggs  and  sperms  already 
contain  a  mixture  of  paternal  and  maternal  chromosomes 
derived  from  the  preceding  generations.  It  does  illustrate, 
however,  the  mixture  of  hereditary  qualities  by  the  sexual 
fusion,  the  domination  of  certain  of  these  qualities,  and  the 
chances  of  resemblances  in  the  progeny.  It  should  be 
understood  also  that  the  structural  resemblance  to  the 
maternal  form  or  to  the  paternal  form  does  not  include  sex 
determination.  For  example,  the  new  individual  which 
resembles  the  maternal  form  may  prove  to  be  either  male 
or  female,  and  vice  versa. 

It  is  evidently  impossible  that  the  chromosomes  con- 
tinue to  be  doubled  at  each  generation,  without  any  reverse 
process  of  reduction.  The  two  cardinal  points  in  every  life- 
history,  therefore,  are  fertilization,  by  means  of  which  the 
chromosomes  are  doubled,  and  reduction,  by  means  of 
which  the  doubled  number  is  halved.  The  reduction  pro- 
cess occurs  at  different  stages  in  the  life-history  in  different 
organisms.  Among  animals,  it  occurs  in  connection  with 
the  formation  of  the  eggs  and  sperms ;  and  therefore  reduc- 
tion and  fertilization  are  practically  consecutive  events. 
In  most  plants,  however,  the  two  processes  are  farther 
apart,  separated  from  one  another  by  two  distinct  indi- 


34 


Heredity  and  Eugenics 


viduals,  one  characterized  by  the  reduced  number  of  chro- 
mosomes and  bearing  the  sex  organs  (hence  called  the 
gametophyte),  the  other  characterized  by  the  doubled  num- 
ber of  chromosomes  and  producing  spores  (hence  called 
the  sporophyte).  In  general,  it  may  be  said  that  among 
animals  reduction  occurs  in  connection  with  gamete  forma- 
tion, while  among  plants  it  occurs 
in  connection  with  spore  formation. 
To  use  the  simpler  illustration 
of  animals,  it  is  evident  that  the 
cells  making  up  the  body  of  an 
individual  contain  the  doubled 
number  of  chromosomes  (Fig.  6, 
i),  derived  from  the  fertilized  egg 
from  which  the  body  developed. 
When  the  sexual  cells  (eggs  or 
sperms)  of  this  individual  are 
formed,  the  reduction  occurs,  and 
the  eggs  or  sperms  contain  the  re- 
duced number.  How  the  maternal 
and  paternal  chromosomes  are  dis- 
tributed in  this  reduction  may  not 
be  clear,  but  it  is  evident  that 

either  eggs  or  sperms  may  contain  chromosomes  derived 
from  either  line  of  descent  (Fig.  6).  In  other  words,  it  is 
not  inconceivable  to  think  of  an  egg  containing  only  chro- 
mosomes derived  from  the  paternal  side,  or  of  a  sperm  con- 
taining only  chromosomes  derived  from  the  maternal  side, 
or  most  likely  of  both  eggs  and  sperms  containing  chromo- 
somes derived  from  both  sides  (Fig.  6,  2-5) . 

These  considerations  indicate  how  every  sexual  fusion 
results  in  a  complex  of  possibilities,  and  the  study  of  heredity 


FIG.  6. — Diagram  illustrat- 
ing result  of  reduction:  i, 
ordinary  cell  of  the  body  con- 
taining doubled  number  of 
chromosomes;  2-5,  eggs  or 
sperms  containing  the  reduced 
number,  and  illustrating  the 
possibilities  in  the  distribu- 
tion of  paternal  (A A)  and 
maternal  (BB)  chromosomes. 


Physical  Basis  of  Heredity  and  Evolution  35 

is  to  discover  whether  these  possibilities  can  be  formulated 
into  a  law. 

In  this  connection,  the  phenomenon  of  parthenogenesis 
should  be  referred  to.  By  definition,  it  means  the  pro- 
duction of  a  new  individual  by  an  unfertilized  egg,  and  it  is 
a  very  common  phenomenon  among  plants.  When  it  is 
remembered  that  ordinary  cells  can  produce  new  individ- 
uals by  vegetative  multiplication,  and  that  spores  can 
reproduce,  it  should  not  be  thought  strange  that  so  well- 
nourished  a  cell  as  the  egg  can  do  the  same  thing.  Among 
the  higher  plants,  however,  in  which  the  whole  mechanism 
has  been  worked  out  in  greater  detail,  there  is  a  significant 
fact  connected  with  the  cases  of  parthenogenesis.  In  every 
case  investigated,  the  reduction  in  connection  with  spore 
formation  has  not  occurred,  and  therefore  the  unfertilized  egg 
contains  the  doubled  number  of  chromosomes,  just  as  though 
it  had  been  fertilized.  In  parthenogenesis,  therefore,  the 
indications  are  that  the  fact  to  be  explained  is  not  reproduc- 
tion by  an  unfertilized  egg,  but  the  failure  of  reduction. 

The  whole  history  of  sexual  reproduction  among  plants 
indicates  that  its  primary  significance  is  not  reproduction, 
for  probably  many  more  individuals  are  produced  by  vege- 
tative multiplication  and  by  spores  than  by  the  sex  act. 
This  would  mean  that  the  sexual  method  is  chiefly  con- 
cerned with  other  results,  which  are  secured  in  connection 
with  reproduction.  These  results  seem  to  be  the  continual 
securing  of  new  combinations,  and  new  combinations  cer- 
tainly make  for  evolutionary  progress. 


WILLIAM  ERNEST  CASTLE 
Professor  of  Zoology,  Harvard  University 


CHAPTER  III 
THE  METHOD  OF  EVOLUTION1 

No  one  today  doubts  the  reality  of  evolution,  at  least 
no  one  does  who  has  had  practical  experience  in  animal  or 
plant  breeding,  and  who  has  seen  new  forms  of  life  come 
into  being  under  his  own  observation  and  guidance.  But 
the  method  of  evolution  is  still  in  doubt.  It  is  known  in 
general,  that  like  begets  like,  but  that  occasionally  it  begets 
unlike,  and  this  may  become  a  new  race.  As  to  how  the 
new  race  is  begotten  we  have  not  got  much  beyond  Darwin; 
indeed  many  of  us  have  not  got  so  far.  For  Darwin  recog- 
nized two  distinct  ways  in  which  new  races  may  arise,  but 
many  biologists  today  insist  that  there  is  only  one  way, 
the  way  in  which  Minerva  was  begotten,  who  "sprang 
full-fledged  from  the  head  of  Jove."  The  modern  name 
for  this  method  of  origin  is  mutation,  and  its  advocates, 
like  the  "followers  of  the  prophet,"  insist  that  there  is  no 
other. 

Darwin  was  well  aware  that  new  races  may  arise  in  this 
way,  particularly  under  domestication,  as  in  the  case  of 
the  Ancon  ram  and  Niata  cattle;  but  he  believed  that  a 
far  commoner  and  more  important  method,  particularly 
among  wild  species,  consists  in  a  slow  and  gradual  modi- 
fication of  the  race,  constantly  in  one  direction,  as  under 
the  ever-growing  power  of  a  hydraulic  press,  until  the 

1  In  these  two  chapters,  especially  in  the  second  (chap,  iv),  material  has  been 
drawn  freely  from  the  writer's  book  on  Heredity  in  Relation  to  Evolution  and  Animal 
Breeding  (D.  Appleton  &  Co.,  New  York),  for  which  he  has  the  kind  permission 
of  the  publishers.  He  also  wishes  to  acknowledge  aid  given  by  the  Carnegie 
Institution  to  the  investigations  herein  described. 

39 


4O  Heredity  and  Eugenics 

descendants  become  so  different  from  their  progenitors 
that  man  assigns  them  to  distinct  races. 

Now  I  am  inclined  to  think  that  Darwin  was  on  the 
whole  nearer  the  truth  than  the  mutationists.  They  have 
perceived  a  half-truth  and  perceived  it  more  clearly  than 
did  Darwin,  but  in  scrutinizing  this  they  have  lost  sight  of 
the  larger  picture  which  he  saw.  Darwin  saw  that  new 
races  arise  in  two  ways,  and  I  shall  attempt  to  show  that 
he  was  right. 

First  let  us  discuss  the  Minerva-like  method  of  evolu- 
tion, the  birth  of  new  races  in  a  day,  a  method  of  great 
theoretical  interest  and  practical  importance.  What  is 
known  about  this  method  of  evolution  is  commonly  called 
Mendelism,  after  Gregor  Mendel,  an  Austrian  monk  of  the 
last  century.  Mendel  was  a  school  teacher  who  studied 
as  well  as  taught,  and  fortunately  for  us  he  studied  from 
the  book  of  nature  more  than  from  other  books.  He 
thought  clearly  about  the  things  he  saw,  but  wrote  little. 
Indeed  we  wish  that  he  had  written  more,  but  perhaps  if 
he  had  done  so  he  would  have  thought  less  well.  Like  most 
profound  thinkers,  he  was  in  advance  of  his  day,  so  that 
when  he  spoke,  the  "wise  men"  of  the  time  failed  to  under- 
stand him.  The  "wise  man"  to  whom  Mendel  hoped  to 
make  his  ideas  plain  was  the  great  German  botanist,  Karl 
Naegeli,  to  whom  Mendel  wrote  a  number  of  letters  about 
his  studies  of  plant  hybrids.  Naegeli  failed  to  grasp  the 
important  point  in  Mendel's  work,  and  the  letters  were  for- 
gotten until  Mendel's  fame  had  become  world-wide.  Then 
they  were  hunted  up  and  published.  Naegeli 's  failure 
to  understand  Mendel  is  after  all  not  surprising;  Mendel's 
thinking  was  in  advance  of  his  time.  Several  biological 
principles  now  considered  commonplaces  were  then  un- 


The  Method  of  Evolution  41 

known.  When  these  had  been  established,  Mendel's  law  was 
independently  rediscovered  long  after  his  death.  All  honor 
to  the  rediscoverers,  DeVries,  Correns,  and  Tschermak, 
that,  honoring  the  all-but-forgotten  monk,  they  called  the 
new-found  law  Mendel's,  rather  than  their  own! 

In  Mendel's  time  little  was  known  about  the  nature  of 
the  reproductive  bodies  from  which  new  individuals  arise, 
or  of  how  these  bodies  are  produced,  or  how  they  differ 
from  the  organisms  which  produce  them.  These  points 
must  be  considered  briefly. 

An  old  but  ever-recurring  question  in  regard  to  heredity 
is  this:  Does  one  generation  inherit  any  part  of  the 
experience  of  the  previous  generation  ?  In  other  words,  is  a 
character  acquired  by  one  generation  inherited  by  the  next  ? 
This  question,  first  raised  in  concrete  form  by  Weismann, 
has  been  discussed  pro  and  con  for  many  years,  but  the  con- 
sensus of  scientific  opinion  at  the  present  time  favors  Weis- 
mann's  idea  that  acquired  characters  are  not  inherited. 
In  forming  a  judgment  on  this  question,  one  fundamental 
fact  should  be  borne  in  mind,  that  in  the  higher  animals 
body  plasm  and  germ  plasm  are  distinct;  that  is,  the  body 
is  distinct  from  the  reproductive  cells  which  it  contains,  and 
out  of  which  the  next  generation  is  produced.  Influences 
which  affect  the  body  have  no  necessary  influence  on  the 
germ  cells. 

Weismann  some  years  ago  demonstrated  this  experi- 
mentally for  mutilations  of  the  body.  When  the  tails  of 
mice  were  cut  off  generation  after  generation,  it  was  found 
that  young  of  the  mutilated  parents  had  tails  as  long  as  other 
mice.  More  distinct  evidence  of  the  independence  of  germ 
plasm  and  body  is  furnished  by  an  experiment  recently 
performed  by  Dr.  Phillips  and  myself. 


42  Heredity  and  Eugenics 

A  young  female  albino  guinea-pig  approaching  sexual 
maturity  was  deprived  of  her  ovaries,  and  into  her  body 
was  introduced  the  living  ovary  of  a  freshly  killed  black 
guinea-pig,  about  three  weeks  old  (Figs.  7  and  8).  She 
was  later  mated  with  an  albino  guinea-pig  (Fig.  9). 
By  him  she  bore  two  litters  of  living  young,  and  died 
pregnant  a  little  over  one  year  after  the  operation,  con- 
taining a  third  litter  (Figs.  10-15).  Had  she  not  been 
operated  upon,  her  young  by  this  male  would  undoubtedly 
have  been  albinos,  for  albino  guinea-pigs  produce  only 
albino  young,  as  several  investigators  have  clearly  shown. 
But  those  young  which  she  did  bear  were  without  exception 
black,  which  character  clearly  they  owed  to  the  fact  that 
they  developed  from  eggs  produced  by  the  ovary  taken  at 
a  very  immature  stage  from  a  black  animal.  From  evi- 
dence such  as  this  it  is  concluded  that  the  inheritance  can 
not  be  affected  by  modifications  of  the  body  of  the  parent, 
not  even  when  the  body  is  completely  changed,  since  the 
body,  so  far  as  heredity  is  concerned,  is  merely  a  container 
of  the  reproductive  cells.  To  modify  the  inheritance  we  must 
modify  the  reproductive  cells. 

But  the  reproductive  cells  are  not  simple;  they  are 
really  dual  in  character,  made  up  of  equivalent  parts 
derived  from  father  and  mother.  On  this  matter  breeding 
experiments  throw  light. 

If  a  black  guinea-pig  of  pure  race  is  mated  with  an 
albino,  the  offspring  are  all  black,  yet  contain  albinism  as 
a  latent  or  recessive  character.  For  if  one  of  these  black 
offspring  is  now  mated  with  the  same  albino,  only  half  of 
the  offspring  are  black,  the  others  being  albinos.  And  if 
two  of  the  cross-bred  blacks  are  mated  with  each  other, 
one-fourth  of  the  young,  on  the  average,  are  albinos,  three- 


-* 

* 


FIG.  7. — A  young,  black  guinea-pig,  about  three  weeks  old.  Ovaries  taken 
from  an  animal  like  this  were  transplanted  into  the  albino  shown  immediately 
below  it. 

FIG.  8. — An  albino  female  guinea-pig.  Its  ovaries  were  removed  and  in 
their  place  were  introduced  ovaries  from  a  black  guinea-pig,  like  the  one  shown 
in  Fig.  7. 

FIG.  9. — An  albino  male  guinea-pig,  with  which  was  mated  the  albino  shown 
in  Fig.  8. 


14 


15 


FIGS.  10-15. — Pictures  of  three  living  guinea-pigs  (10-12)  and  of  the  pre- 
served skins  of  three  others  (13-15),  all  of  which  were  produced  by  the  pair  of 
albinos  shown  in  Figs.  8  and  Q. 


The  Method  of  Evolution  45 

fourths  being  black  (Figs.  16-19).  This  result  is  explained 
in  the  following  way.  The  cross-bred  black  individual 
received  from  its  black  parent  the  character  black  (B\ 
and  from  its  white  parent  the  character  white  (W}.  In  it 
accordingly  black  and  white  were  associated  together,  but 
only  the  former  was  manifested,  the  white  remaining  hidden 
by  the  black.  But  in  reproduction  the  cross-bred  black 
individual  transmits  black  and  white  in  separate  cells. 
And  since  these  two  kinds  of  cells  are  in  the  long  run  equally 
numerous,  it  follows  that  the  cross-bred  black  individuals 
produce  both  black  and  white  offspring  in  proportions  fairly 
constant  (Fig.  20). 

Inheritance  of  this  sort  is  called  Mendelian,  after  Gregor 
Mendel  who  first  observed  and  explained  it.  The  law 
governing  such  inheritance  is  called  Mendel's  law.  Such 
inheritance  is  satisfactorily  accounted  for  by  the  assump- 
tion that  the  reproductive  cells  are  at  first  dual  hi  nature, 
but  become  simple  before  they  can  function  in  the  pro- 
duction of  a  new  individual.  For  this  assumption  we  have 
abundant  evidence  furnished  by  the  direct  study  of  the 
reproductive  cells  with  the  microscope.  These  cells,  like 
the  cells  of  the  body  in  which  they  are  contained,  show  in 
their  nuclei  at  cell  division  a  fairly  constant  number  of 
bodies  known  as  chromosomes.  In  the  worm  Ascaris  there 
are  only  2  of  these  chromosomes;  in  the  sea-urchin  Toxo- 
pneustes  there  are  36;  in  mice  and  men,  about  24. 

A  new  individual  arises,  in  sexually  produced  animals, 
out  of  the  union  of  an  egg  with  a  sperm.  The  sperm  is 
relatively  small,  but  its  influence  equals  that  of  the  much 
larger  egg,  which  fact  throws  light  on  the  nature  of  the 
material  basis  of  heredity.  It  suggests,  namely,  that 
this  material  consists  largely  of  ferment-like  bodies  which 


Heredity  and  Eugenics 


The  Method  of  Evolution  47 

initiate  specific  metabolic  processes  in  a  suitable  medium 
represented  by  the  larger  portion  of  the  egg. 

In  egg  and  sperm,  before  their  union,  the  chromosome 
number  is  reduced  one-half,  from  the  double  to  the  single 
condition;  in  Ascaris,  from  2  to  i;  in  the  sea-urchin,  from 
36  to  18;  in  the  mouse  and  in  the  man  from  24  to  12. 
These  reductions  occur  in  what  is  called  the  maturation 
of  the  sexual  products. 

In  the  male,  the  primitive  germ  cell  containing  the 
double  or  2N  number  of 
chromosomes  divides  up 
into  a  group  of  four  cells, 
each  containing  the  single  or 
N  number  of  chromosomes. 
This  comes  about  by  a  fail- 
ure of  the  chromosomes  to 
split  at  one  of  the  two  cell 
divisions  which  produce  the 
group  of  four  sperm  cells, 

as    they   regularly    do    Ul          FIG.  20 —Diagram  to  explain  the  result 
,.  ,,      ,.    .  .  shown  in  Figs.  1 6-iQ. 

ordinary  cell   division.     A 

tadpole-like  sperm  now  arises  from  each  of  the  cells  con- 
taining the  reduced  number  of  chromosomes. 

In  the  maturation  of  the  egg,  reduction  is  likewise 
accomplished  by  two  cell  divisions,  hi  one  of  which  the 
chromosomes  do  not  split  as  in  ordinary  cell  divisions. 
The  divisions  of  the  egg,  however,  are  into  parts  of  very 
unequal  size,  only  one  of  which  is  fertilized,  the  rest  failing 
to  develop.  For  example,  in  the  marine  worm  Nereis, 
according  to  Wilson,  the  maturation  of  the  egg  occurs 
simultaneously  with  its  fertilization.  The  first  maturation 
division  separates  off  a  minute  cell,  known  as  the  first  polar 


48  Heredity  and  Eugenics 

body,  and  is  quickly  followed  by  a  second  likewise  unequal 
division,  by  which  a  second  polar  body  is  produced.  The 
number  of  chromosomes  remaining  in  the  egg  nucleus  is 
now  reduced  to  half  that  in  the  egg  before  maturation.  A 
sperm  entering  the  egg  has  formed  within  it  a  second  nuclear 
body  which,  like  that  of  the  egg  contains  a  reduced  number 
of  chromosomes.  By  the  union  of  these  two  nuclei  a  new 
nucleus  is  formed  which  contains  the  double  number,  and 
from  this  all  cells  of  the  new  individual  are  directly  derived. 
In  all  such  cells  the  double  chromosome  number  is  present. 
Similar  events  take  place  in  the  maturation  and  fertilization 
of  animal  eggs  in  general. 

Now,  when  the  egg  of  a  black  guinea-pig  is  fertilized  with 
the  sperm  of  a  white  one,  or  vice  versa,  protoplasmic  con- 
stituents unite  which  in  one  case  are  able  to  produce  a 
black  coat,  in  the  other  a  white  one.  These  constituents, 
whatever  they  are,  evidently  separate  from  each  other  and 
pass  into  different  cell  products  when  the  germ  cells  of  the 
cross-bred  individual  ripen.  It  seems  natural  to  suppose 
that  the  separation  occurs  at  the  reduction  of  the  chromo- 
somes from  the  double  to  the  single  condition.  Half  the 
sperms,  accordingly,  of  the  cross-bred  black  individual  bear 
black,  half  white,  none  both;  and  the  same  is  true  of  the 
eggs  (Fig.  20).  Experiment  proves  conclusively  that  this  is 
so.  Blackness  and  whiteness  behave  in  crosses  like  indi- 
visible units.  They  may  be  brought  together  repeatedly 
in  crosses,  but  always  separate  again  at  the  maturation  of 
the  gametes.  We  call  them  unit-characters.  Black  is  a 
positive  unit  (presence  of  black  pigment),  white  its  corre- 
sponding negative  (absence  of  black  pigment). 

Other  unit-characters  are  quite  independent,  in  their 
inheritance,  of  black  and  white.  Thus,  the  coat  of  a 


The  Method  of  Evolution 


49 


Heredity  and  Eugenics 


.M    g     > 

V-  o  '55 


u.  ' 


JJ    «  3T  _C 

<  <  2  *>> 

I  C  73 

I  •—    rf 


o   o 

—  — 


•i 

tc    — . 

"5*  ci 

^  s 


O     O 


M      W 

o  o 


The  Method  of  Evolution  51 

guinea-pig  may  be  either  rough  or  smooth  (Figs.  21-24). 
Rough  is  a  unit-character  dominant  over  smooth  in  crosses, 
and  among  the  second  generation  offspring  from  such  a  cross 
occur  three  rough  individuals  to  one  smooth  one.  If  the 
rough  parent  is  white  (Fig.  23)  and  the  smooth  one  dark 
(Fig.  21),  the  parents  differ  in  two  unit-characters,  and  the 
sequel  shows  that  these  are  independent  units.  For 
although  the  immediate  offspring  are  all  dark  and  rough 
(Fig.  24),  the  next  generation  contains  four  sorts  of  indi- 
viduals, representing  all  possible  combinations  of  the  two 
alternative  pairs  of  units:  (i)  smooth  dark,  like  one  grand- 
parent (Fig.  21);  (2)  rough  white,  like  the  other  (Fig.  23); 
(3)  rough  dark,  like  the  parents  (Fig.  24) ;  and  (4)  smooth 
white,  a  new  combination  (Fig.  22). 

Again,  length  of  the  hair  is  independent  of  its  color  or 
roughness  (Figs.  25-27).  A  short-haired  colored  animal 
mated  with  a  long-haired  white  one  produces  only  short- 
haired  colored  offspring,  which,  bred  inter  se,  produce  hi 
the  next  generation  young  of  four  sorts:  (i)  long  white, 
(2)  short  dark,  (3)  long  dark,  and  (4)  short  white. 

Recombinations  in  such  ways  can  be  accounted  for  if 
we  suppose  each  different  unit-character  to  have  its  basis 
in  a  different  material  body  within  the  cell,  perhaps  in  a 
different  chromosome  or  part  chromosome.  Thus,  suppose 
hair  length  to  have  its  basis  in  one  cell  structure,  which  we 
may  represent  in  a  diagram  (Fig.  29)  by  a  circle,  and  sup- 
pose hair  color  to  have  its  basis  in  another  cell  structure 
represented  by  a  square,  and  suppose  further  that  these 
two  structures  are  independent  of  each  other  in  their  fusions 
and  segregations;  then  if  we  cross  a  long-haired  white  (L  W) 
animal  with  a  short-haired  dark  one  (SD\  a  combina- 
tion (or  zygote)  will  be  formed  showing  only  the  dominant 


Heredity  and  Eugenics 


characters,  short  and  dark  hair,  but  able  to  transmit  the 
alternative  conditions,  long  and  white  hair.  At  repro- 
duction by  such  an  individual,  L  will  separate  from  S,  and 
W  will  separate  from  D,  passing  into  a  different  cell  prod- 
uct, but  it  will  be  a  matter  of  chance  whether  L  is  asso- 
ciated with  W  as  originally,  or  with  D.  Hence  the  chances 
are  even  for  the  production  of  the  four  kinds  of  gametes 
shown  in  the  diagram,  LW,  SD,  LD,  and  SW,  the  visible 

expression  of  which  would 
produce  individuals  in 
character,  respectively  long 
white,  short  dark,  long  dark, 
and  short  white,  as  actually 
obtained  by  experiment. 

If  the  individuals  crossed 
are  pure  and  differ  in  three 
particulars,  color,  length, 
and  roughness  of  the  coat, 
then  their  grandchildren 
will  be  of  eight  sorts,  repre- 
senting all  possible  combi- 
nations of  three  independent  unit-character  pairs,  each  of 
which  has  its  basis  in  a  different  material  body  in  the  cell. 
A  great  many  of  the  characters  of  animals  and  plants 
behave  as  simple  units  in  heredity,  yielding  a  3 :  i  ratio  of 
dominant  to  recessive  individuals  in  the  second  genera- 
tion from  the  cross.  I  have  shown  that  this  is  true  of 
certain  hair  characters  in  guinea-pigs,  namely,  blackness, 
roughness,  and  length  of  the  hair.  We  have  no  idea  how 
numerous  such  characters  are  until  they  happen  to  be  lost 
in  one  individual  or  another.  Then  a  new  variation,  a 
sport  or  mutation,  is  observed.  It  is  by  this  means,  acci- 


FIG.  29. — Diagram  to  show  the  result 
of  crossing  a  long-haired,  white  guinea- 
pig  (L  W)  with  a  short-haired,  dark  one 
(SD). 


The  Method  of  Evolution  53 

dental  loss  of  simple  unit-characters,  that  the  great  color 
variation  of  domesticated  animals  has  arisen. 

We  should  naturally  consider  the  color  character  of  a 
wild  mouse,  rat,  or  rabbit,  to  be  very  simple,  for  we  observe 
such  animals  to  breed  very  true  to  color,  but  the  behavior 
of  the  wild  type  in  crosses  shows  it  in  reality  to  be  very  com- 
plex, and  to  be  the  result  of  the  simultaneous  presence 
of  some  half-dozen  or  more  wholly  independent  unit- 
characters.  New  color  varieties  have  arisen  by  loss  or  modifi- 
cation of  one  or  more  of  these  unit-characters.  For  example, 
the  wild  house  mouse  by  simple  loss  of  three  independent 
factors  has  given  rise  to  seven  additional  varieties  known 
among  fancy  mice. 

The  gray  fur  contains  black,  brown,  and  yellow  pig- 
ments disposed  in  a  definite  pattern  in  the  individual  hairs. 
Loss  of  this  pattern  alone  produces  the  black  variety.  Loss 
of  black  produces  the  cinnamon  variety;  loss  of  both  pro- 
duces the  brown  or  chocolate  variety.  Loss  of  the  power 
to  produce  color,  that  is  loss  of  some  general  color  factor, 
produces  an  albino,  whose  breeding  capacity  will  vary  with 
the  number  of  other  factors  which  it  retains.  Several  other 
color  factors  occur  in  mice,  the  loss  of  which  has  produced 
new  series  of  color  varieties,  but  these  will  suffice  to  show 
the  process  by  which  new  varieties  arise  through  loss  of 
unit-characters. 

Simple  unit-characters  are  not  confined  to  the  super- 
ficial parts  of  an  animal,  as  for  example  to  its  fur.  We 
know  these  superficial  characters  best  probably  simply 
because  they  are  most  easily  observed. 

Loss  of  horns  in  cattle  behaves  as  a  dominant  unit- 
character;  likewise  in  man  a  shortened  condition  of  the 
skeleton  producing  two-jointed  instead  of  three-iointed 


54  Heredity  and  Eugenics 

fingers  behaves  as  a  simple  dominant  unit-character.  A 
curious  affection  of  the  nervous  system  producing  the 
waltzing  condition  of  Japanese  mice,  behaves  as  a  recessive 
unit-character  in  crosses  with  the  normal  condition. 

Is  all  inheritance  unit-character  inheritance?  This 
question  cannot  at  present  be  answered  fully,  but  many 
facts  indicate  that  it  is.  A  large  class  of  seemingly  uncon- 
formable  cases  which  presented  the  greatest  obstacle  to  such 
a  view  has  recently  been  brought  into  line  with  the  unit- 
character  hypothesis.  I  refer  to  cases  of  blending  inherit- 
ance, in  which  the  offspring  are  intermediate  between  the 
parents,  and  this  intermediate  condition  persists  into  the 
next  generation. 

Size  and  skeletal  proportions  are  inherited  apparently 
in  this  fashion.  It  is  possible,  however,  that  even  in  such 
cases  unit-character  segregations  may  really  occur,  though 
their  presence  is  obscured  because  dominance  does  not  occur. 
For  in  plants  such  size  segregations  have  been  observed 
recently  by  my  colleague  Dr.  East  and  by  others. 

A  single  illustration  will  suffice.  When  varieties  of  maize 
(or  Indian  corn)  are  crossed  which  differ  in  size  of  ear, 
the  hybrid  plants  bear  ears  of  intermediate  size  but  not 
more  variable  than  the  more  variable  parent.  The  second 
generation  offspring,  however,  are  extremely  variable, 
ranging  in  size  from  that  of  the  smaller  parent  variety  to 
that  of  the  larger. 

The  peculiarity  of  what  we  have  called  blending 
inheritance  lies  partly  in  the  entire  absence  of  dominance. 
In  blending  inheritance  a  unit-character  represented  once 
in  the  fertilized  egg  has  only  half  as  much  effect  as  one  rep- 
resented twice.  In  color  inheritance,  usually,  but  not  always, 
a  single  dose  of  a  unit-character  is  as  effective  as  a  double 


The  Method  of  Evolution  55 

dose  in  causing  the  development  of  the  character.  In  size 
inheritance,  however,  the  single  and  double  doses  probably 
produce  very  different  effects. 

A  further  apparent  difficulty  encountered  in  interpreting 
blending  inheritance  as  unit-character  inheritance  lies  in 
the  multiplicity  of  the  units  involved,  so  that  segregations 
do  not  occur  into  a  few  discontinuous  size  classes,  but  into 
classes  so  numerous  and  differing  so  little  from  each  other 
that  it  is  very  difficult  to  distinguish  them. 

Suppose  that  in  crosses  of  black  with  white  guinea-pigs, 
black  were  represented  by  two  unit-characters  B  and  Bf, 
instead  of  by  one,  residing  perhaps  in  different  chromosomes, 
and  that  either  one  of  these  could  by  itself  produce  black 
color,  then  a  larger  proportion  than  three-fourths  of  the 
second  generation  offspring  would  be  black,  namely,  fir- 
If,  further,  the  presence  of  a  larger  number  of  factors  for 
black  produced  more  black  pigment  in  the  fur  than  a  smaller 
number  produced,  then  we  should  have  gradations  of  black- 
ness among  the  second  generation  offspring  as  follows: 
4,  3,  2,  i,  o. 

Add  a  third  factor  for  black  in  the  supposed  cross, 
located  perhaps  in  a  third  chromosome,  and  the  pure  whites 
would  be  reduced  to  i  to  64  of  the  second  generation  off- 
spring, while  the  different  gradations  or  intensities  of  black- 
ness would  become  6,  5,  4,  3,  2,  i,  o.  The  occasional  white 
individual  would  now  differ  so  little  from  the  lightest  black 
one  that  the  two  might  often  be  confused,  and  there  would 
seem  to  exist  all  intermediate  stages  between  pure  white 
and  pure  black,  without  entire  segregation  into  either.  By 
selecting  for  the  lightest  or  the  darkest  condition  within  a 
mixed  race  of  such  second  generation  offspring  one  would 
obtain  with  each  selection  a  larger  proportion  of  extremely 


56  Heredity  and  Eugenics 

dark  or  extremely  light  individuals,  until  a  pure  race  was 
obtained.  Further,  if  the  black  character  should  become 
attached  to  additional  material  bodies  in  the  cell  (chromo- 
somes or  the  like),  so  that  it  would  be  represented  by  addi- 
tional units,  then  the  occurrence  of  light-colored  progeny 
would  become  still  rarer,  and  deeper  intensities  of  black- 
ness than  before  existed  would  now  occur.  Thus  selection 
would  become  a  means  for  the  modification  of  a  character 
really  dependent  upon  the  inheritance  of  unchanging  units. 
Now  this  is  perhaps  what  occurs  when  one  seeks  to  modify 
size  by  selection. 

There  are  strong  reasons  for  believing  that  mendelizing 
characters  can  be  modified  by  selection,  though  this  idea 
is  vigorously  denied  by  many  Mendelians,  as  for  example 
by  Johannsen.  In  Johannsen's  view,  selection  can  do 
nothing  but  sort  out  variations  already  existing  in  a  race. 
I  prefer  to  think  with  Darwin  that  selection  can  do  more 
than  this,  that  it  can  heap  up  quantitative  variations  until 
they  reach  a  sum  total  otherwise  unattainable,  and  that 
it  thus  becomes  creative.  I  will  describe  briefly  certain 
experiences  of  my  own  which  support  this  idea. 

In  several  cases  I  have  observed  characters  at  first  feebly 
manifested  gradually  improve  under  selection  until  they 
became  established  racial  traits.  Thus  in  guinea-pigs,  the 
hind-foot  commonly  bears  three  toes  (Fig.  30,  A).  But 
several  years  ago  I  observed  an  individual  which  had  an 
imperfectly  developed  fourth  toe,  similar  to  that  shown  in 
Fig.  30,  C.  From  the  descendants  of  this  animal,  obtained 
by  inbreeding  and  selection,  was  formed  a  race  having 
well-developed  fourth  toes  (Fig.  30,  B)  on  both  hind 
feet.  The  extra  toe  made  its  appearance  poorly  devel- 
oped on  the  left  foot  only.  About  6  per  cent  of  the 


The  Method  of  Evolution  57 

offspring  of  this  animal  by  normal  unrelated  mothers  were 
polydactylous,  but  among  his  offspring  were  some  with 
better  developed  fourth  toes  than  the  father  possessed. 
Such  individuals  were  selected  throughout  five  successive 
generations,  at  the  end  of  which  time  a  good  four-toed  race 
had  been  established.  It  was  found  in  general  that  those 
animals  which  had  best-developed  fourth  toes  transmitted 
the  character  most  strongly  in  crosses  with  unrelated  normal 
animals.  The  percentage  of  polydactylous  individuals 
produced  in  such  crosses  varied  all  the  way  from  o  to  100 


FIG.  30. — A,  hind-feet  of  an  ordinary  guinea-pig;  B,  of  a  four-toed  guinea- 
pig;  C,  of  an  imperfectly  four-toed  guinea-pig. 

per  cent.  By  selection  this  percentage  was  increased,  as 
was  also  the  degree  of  development  of  the  fourth  toe  in 
crosses. 

Another  character  which  made  its  appearance  among 
our  guinea-pigs,  at  first  feebly  expressed,  was  a  silvering  of 
the  colored  fur,  due  to  interspersing  of  white  hairs  with  the 
colored  ones  (Fig.  28).  The  first  individuals  observed 
to  have  this  character  bore  white  hairs  on  the  under  surface 
of  the  body  only.  By  inbreeding,  a  homozygous  strain  of 
the  silvered  animals  was  soon  obtained,  one  in  which  all  the 
offspring  were  silvered  to  a  greater  or  less  extent.  Selection 


58  Heredity  and  Eugenics 

was  now  directed  toward  two  ends:  (i)  to  secure  animals 
which  were  free  from  spots  of  red  or  white,  a  condition 
which  was  present  in  the  original  stock;  and  (2)  to  secure 
extensive  and  uniform  silvering  on  a  black  background. 
In  both  these  objects  good  progress  has  been  made.  We 
have  animals  which  are  silvered  all  over  the  body  except 
on  a  part  of  the  head,  and  the  percentage  of  such  well- 
silvered  individuals  is  relatively  high. 

A  more  extensive  selection  experiment  is  one  in  which 
I  have  been  assisted  by  Dr.  John  C.  Phillips  (Figs.  31  and32). 


-3.          -1  0         l+l 


FIG.  31. — Diagram  showing  variation  in  the  color  pattern  of  hooded  rats. 
Numerals  indicate  arbitrary  grades  used. 

Selection  in  this  case  has  been  directed  toward  a  modifica- 
tion of  the  color  pattern  of  hooded  rats,  a  pattern  which  is 
known  to  behave  as  a  recessive  Mendelian  character  in 
crosses  with  either  the  self  (totally  pigmented)  condition 
or  the  so-called  Irish  (white  bellied)  condition  found  in 
some  other  rats.  The  extreme  range  of  variation  among 
our  hooded  rats  at  the  outset  of  this  experiment  is  indicated 
by  the  grades  —2  and  +3  of  Fig.  31.  Selection  was  now 
made  of  the  extreme  variates  in  either  direction  and  these 
were  bred  separately.  Two  series  of  animals  were  thus 


The  Method  of  Evolution 


59 


established:  one  of  narrow-striped  animals,  minus  series; 
the  other  of  wide  striped,  plus  series.  In  each  generation 
the  most  extreme  individuals  were  selected  as  parents;  in 
the  narrow  series,  those  with  narrowest  stripe;  in  the  wide 
series,  those  with  widest  stripe. 


+3 


-1 


Generation     12345678 

FIG.  32. — Chart  showing  effects  of  selection  in  eight  successive  generations 
upon  the  color  pattern  of  hooded  rats.  A,  A',  average  condition  of  selected 
parents;  B,  B',  of  their  offspring. 

The  result  of  the  selection  is  shown  graphically  in  Fig. 
32  (compare  Table  I).  The  offspring  in  the  narrow  series 
became  with  each  generation  narrower;  those  in  the  wide 
series  became  with  each  generation  wider,  with  a  single 
exception.  In  the  second  generation  the  wide  stock  was 
enlarged  by  the  addition  of  a  new  strain  of  animals.  This 
caused  a  temporary  falling  off  in  the  average  grade  of  the 
young,  the  two  series  overlapping  for  that  generation.  No 


6o 


Heredity  and  Eugenics 


new  stock  was  at  any  other  time  introduced  in  either  series, 
the  two  remaining  distinct  at  all  times  except  in  the  second 
generation.  It  will  be  observed  that  a  change  in  the  aver- 
age grade  of  the  parents  is  attended  by  a  corresponding 
change  in  the  average  of  the  offspring,  and  likewise  in  the 
range  of  variation  in  the  offspring.  The  amount  of  varia- 
bility of  the  offspring  is  not  materially  affected  by  the 
selection,  but  the  average  about  which  variation  occurs  is 
steadily  changed,  as  are  also  the  limits  of  the  range  of 
variation. 

TABLE  I 

RESULTS  OF  SELECTION  FOR  MODIFICATION  OF  THE   COLOR-PATTERN  OF 
HOODED  RATS 


Generation 

Average  Grade 
Parents 

Average  Grade 
Offspring 

Number  of 
Offspring 

Plus  series 

I  

2.50 

2  .05 

ISO 

2           .         

2  .  SI 

I   02 

471 

7 

2  .  73 

2  .  SI 

341 

4.  . 

3  .00 

2.  72 

•144 

S.  . 

3-33 

2  .90 

610 

6     

•i  .  ci 

?    OO 

834 

7.  . 

I  .  S3 

3  .  14. 

874 

8  

3.6s 

3  •  3O 

QI 

Total  .  . 

3,815 

Minus  series 

i  

i  .46 

I  .OO 

ss 

2  

i  .41 

I  .07 

132 

3.  . 

i.<;6 

1.18 

IQ5 

4  

i  .69 

1.28 

320 

S.  . 

i  .73 

I  -41 

701 

6  

1.86 

I.S6 

I.2S2 

7.  . 

2  .OO 

I  .  7O 

I.S44 

8  

2  .03 

1.78 

713 

Total  . 

4,021 

The  interesting  feature  of  this  experiment  is  the  pro- 
duction, as  a  result  of  selection,  of  wholly  new  grades,  in 
the  narrow  series  of  animals  having  less  pigment  than  any 
known  type  other  than  the  albino;  in  the  wide  series,  of 


The  Method  of  Evolution  61 

animals  so  extensively  pigmented  that  they  would  readily 
pass  for  the  "Irish  type,"  which  has  white  on  the  belly 
only,  but  which  is  known  to  be  in  crosses  a  Mendelian  alter- 
native to  the  hooded  type.  By  selection  we  have  practi- 
cally obliterated  the  gap  which  originally  separated  these 
types,  though  selected  animals  still  give  regression  toward 
the  respective  types  from  which  they  came.  But  this 
regression  grows  less  with  each  successive  selection  and  ulti- 
mately should  vanish,  if  the  story  told  by  these  statistics 
is  to  be  trusted.  As  yet  there  is  no  indication  that  a  limit 
to  the  effects  of  selection  has  been  reached. 

From  the  evidence  in  hand  we  conclude  that  Darwin 
was  right  in  assigning  great  importance  to  selection  in 
evolution;  that  progress  results  not  merely  from  sorting 
our  particular  combinations  of  large  and  striking  unit- 
characters,  but  also  from  the  selection  of  slight  differences 
in  the  potentiality  of  gametes  representing  the  same  unit- 
character  combinations. 

Accordingly  we  conclude  that  unit-characters  are  not 
unchangeable.  They  can  be  modified,  and  these  modifica- 
tions come  about  in  more  than  a  single  way.  Occasionally 
a  unit-character  is  lost  altogether  or  profoundly  modified 
at  a  single  step.  This  is  mutation.  But  more  frequent 
and  more  important,  probably,  are  slight,  scarcely  notice- 
able modifications  of  unit-characters  that  afford  a  basis  for 
a  slow  alteration  of  the  race  by  selection.  Mutation,  then, 
is  true,  but  it  is  a  half-truth;  selection  is  the  other  and 
equally  important  half  of  the  truth  of  evolution,  as  Darwin 
saw  it  and  as  we  see  it. 


CHAPTER  IV 

HEREDITY   AND   SEX1 

The  value  of  a  domesticated  animal  often  depends  in 
considerable  measure  on  its  sex.  Therefore,  if  a  means 
could  be  devised  for  controlling  the  sex  of  offspring,  it 
would  be  of  great  economic  value  to  the  breeder.  Endless 
attempts  have  been  made  to  do  this,  and  occasionally  a 
claim  of  success  has  been  made,  but  none  of  these  claims 
has  withstood  the  test  of  critical  analysis  or  experiment. 
The  hypotheses  advanced  to  explain  how  sex  may  be  con- 
trolled have  been  of  the  most  varied  character.  In  some 
the  determination  of  sex  has  been  supposed  to  inhere  in  the 
nature  of  the  parents,  in  others  it  is  referred  to  conditions 
of  the  gametes  themselves. 

Relative  age  or  vigor  of  the  parents  has  been  supposed 
to  influence  sex  in  various  ways.  The  same  idea  has  been 
advanced  regarding  the  gametes  themselves,  it  being 
supposed  that  early  or  late  fertilization  of  the  egg  might 
influence  its  sex.  Experimental  evidence,  however,  as  to 
these  several  hypotheses  is  wholly  negative,  when  one  elimi- 
nates other  possible  factors  from  the  experiment.  Every- 
thing points  to  the  conclusion  that  sex  rests  in  the  last 

1  In  reading  this  chapter,  the  following  definitions  should  be  kept  in  mind. 

Gamete:  a  mature  reproductive  cell  capable,  on  uniting  with  another  gamete, 
of  forming  a  new  individual. 

Zygote:  the  new  individual  formed  by  the  union  of  two  gametes. 

Homozygote:  an  individual  formed  by  the  union  of  two  gametes  of  like  char- 
acter as  regards  heredity 

Heterozygote:  an  individual  formed  by  the  union  of  two  gametes  of  unlike 
character  as  regards  heredity. 

62 


Heredity  and  Sex  63 

analysis  upon  gametic  differentiation,  just  as  the  color  of  a 
guinea-pig  in  a  mixed  race  of  blacks  and  whites  depends 
upon  whether  the  gametes  which  unite  to  produce  it  carry 
black  or  white.  As  the  heterozygous  black  guinea-pig 
forms  black-producing  and  white-producing  gametes  in 
equal  numbers,  so  there  is  reason  to  think  male-producing 
and  female-producing  gametes  are  formed  in  equal  numbers 
by  the  parent,  in  many  cases  at  least.  But  is  it  not  possible 
that  there  may  exist  individuals  which  produce  the  two 
sorts  of  gametes  in  unequal  numbers,  and  so  would  have  a 
tendency  to  produce  more  offspring  of  one  sex  than  of  the 
other  ?  Perhaps  so,  though  we  have  no  evidence  that  such 
a  condition,  if  it  does  exist,  is  transmitted  from  one  genera- 
tion to  another.  On  this  point  I  made  experimental 
observations  upon  guinea-pigs,  extending  over  a  series  of 
years.  Oftentimes  I  found  an  individual  that  produced 
more  offspring  of  one  sex  than  of  the  other,  but  this  was 
probably  due  merely  to  chance  deviations  from  equality. 
I  could  get  no  evidence  that  the  condition  was  inherited, 
though  the  experiment  was  continued  through  as  many 
as  seven  generations,  including  several  hundred  offspring. 
The  essential  difference  between  a  female  and  a  male 
individual  is  that  one  produces  eggs,  the  other  sperm.  All 
other  differences  are  secondary  and  dependent  largely  upon 
the  differences  mentioned.  If  in  the  higher  animals  (birds 
and  mammals)  the  sex  glands  (i.e.,  the  egg-producing  and 
sperm-producing  tissues)  are  removed  from  the  body,  the 
superficial  differences  between  the  sexes  largely  disappear. 
In  insects,  however,  the  secondary  sex-characters  seem  to 
be  for  the  most  part  uninfluenced  by  presence  or  absence 
of  the  sex  glands.  Their  differentiation  occurs  independ- 
ently though  simultaneously  with  that  of  the  sex  glands. 


64  Heredity  and  Eugenics 

The  egg  or  larger  gamete  (the  so-called  macro-gamete) 
in  all  animals  is  non-motile  and  contains  a  relatively  large 
amount  of  reserve  food  material  for  the  maintenance  of  the 
developing  embryo.  This  reserve  food  material  it  is  the 
function  of  the  mother  to  supply.  In  the  case  of  some 
animals,  for  example  flatworms  and  mollusks,  the  food 
supply  of  the  embryo  is  not  stored  in  the  egg  cell  itself,  but 
in  other  cells  associated  with  it,  and  which  break  down  and 
supply  nourishment  to  the  developing  embryo  derived  from 
the  fertilized  egg.  Again,  as  in  the  mammals,  the  embryo 
may  derive  its  nourishment  largely  from  the  maternal 
tissues,  the  embryo  remaining  like  a  parasite  within  the 
maternal  body  during  its  growth,  feeding  by  absorption. 
But  in  all  cases  alike  the  mother  supplies  the  larger  gamete 
and  the  food  material  necessary  to  carry  the  zygote  through 
its  embryonic  stages.  The  father,  on  the  other  hand, 
furnishes  the  bare  hereditary  equipment  of  a  gamete,  with 
the  motor  apparatus  necessary  to  bring  it  into  contact  with 
the  egg  cell,  but  without  food  for  the  developing  embryo  pro- 
duced by  fertilization.  The  gamete  furnished  by  the  father 
is  therefore  the  smaller  gamete,  the  so-called  micro-gamete. 

From  the  standpoint  of  metabolism,  the  female  is  the 
more  advanced  condition;  the  female  performs  the  larger 
function,  doing  all  that  the  male  does  in  furnishing  the 
material  basis  of  heredity  (a  gamete),  and  in  addition 
supplying  food  for  the  embryo.  As  regards  the  reproduc- 
tive function,  the  female  is  the  equivalent  of  the  male 
organism,  plus  an  additional  function,  that  of  supplying 
the  embryo  with  food.  When  we  come  to  consider  the 
structural  basis  of  sex,  we  find  reasons  for  thinking  that 
here,  too,  the  female  individual  is  the  equivalent  of  the 
male  plus  an  additional  element.  The  conclusion  has  very 


Heredity  and  Sex  65 

naturally  been  drawn  that  if  a  means  could  be  devised  for 
increasing  the  nourishment  of  the  egg  or  embryo,  its  develop- 
ment into  a  female  should  be  thereby  insured,  while  the 
reverse  treatment  should  lead  to  the  production  of  a  male. 
But  in  practice  this  a-priori  expectation  is  not  fulfilled. 
Better  nourishment  of  the  mother  may  lead  to  the  produc- 
tion of  more  eggs,  but  not  of  more  female  offspring,  as  has 
repeatedly  been  demonstrated  by  experiment.  Also  poor 
nutrition  of  the  mother  may  diminish  the  number  of  eggs 
which  she  liberates,  but  will  not  increase  the  proportion 
of  males  among  the  offspring  produced. 

An  excellent  summary  of  evidence  on  this  point  was 
made  by  Cuenot  in  1900.  Attempts  to  influence  the  sex 
of  an  embryo  or  larva  by  altered  nutrition  of  the  embryo 
or  larva  itself  have  proved  equally  futile.  Practically  the 
only  experimental  evidence  of  value  in  favor  of  this  idea 
has  been  derived  from  the  study  of  insects,  and  this  is 
capable  of  explanation  on  quite  different  grounds  from 
those  which  first  suggest  themselves.  It  has  sometimes  been 
observed,  as  by  Mary  Treat  for  example,  that  a  lot  of  insects 
poorly  fed  produce  an  excess  of  males.  In  such  lots,  how- 
ever, the  mortality  is  commonly  high,  and  more  females  die 
than  males,  because  the  female  is  usually  larger  and  requires 
more  food  to  complete  its  development.  The  fallacy  in 
concluding  from  such  evidence  that  scanty  nutrition  causes 
individuals  which  would  otherwise  become  females  to 
develop  into  males  was  indicated  years  ago  by  Riley. 
Nevertheless  an  argument  for  the  artificial  control  of  sex 
based  on  such  evidence  is  from  time  to  time  brought  forward, 
as,  for  example,  a  few  years  since  by  Schenk.  The  latest 
advocate  of  sex  control  by  artificial  means  is  an  Italian. 
Russo  (1909).  He  claims  in  the  case  of  rabbits  that  by 


66  Heredity  and  Eugenics 

feeding  the  mother  on  lecithin  or  by  injections  of  lecithin, 
the  proportion  of  female  births  may  be  increased.  His 
evidence  in  support  of  this  claim  is,  however,  wholly  inade- 
quate, and  two  independent  repetitions  of  his  experiments, 
made  by  Basil  in  Italy  and  by  Punnett  in  England,  have 
given  entirely  negative  results. 

An  alternative  hypothesis  concerning  the  determination 
of  sex  has  been  steadily  gaining  ground  during  the  last  ten 
years,  that  sex  has  its  beginning  in  gametic  differentiation 
and  is  finally  determined  beyond  recall  in  the  fertilized 
egg  by  the  nature  of  the  uniting  gametes.  Instructive  in 
this  connection  is  a  study  of  parthenogenesis,  reproduction 
by  unfertilized  eggs.  But  before  entering  upon  this,  it 
may  be  well  to  review  briefly  the  changes  which  regularly 
take  place  in  the  egg  which  is  to  be  fertilized,  and  compare 
with  this  the  changes  which  occur  in  eggs  not  to  be  fertilized. 

In  each  cell  of  the  ordinary  animal  there  occurs  a  charac- 
teristic number  of  bodies  called  chromosomes.  We  do  not 
know  that  they  are  any  more  important  than  other  cell 
constituents,  but  we  know  their  history  better.  These  are 
contained  in  the  nucleus  of  the  cell,  and  at  the  time  of 
nuclear  division  they  are  found  at  the  equator  of  the  division 
spindle.  There  each  of  them  regularly  splits  in  two,  and 
one  derivative  goes  to  either  end  of  the  spindle,  and  so  into 
one  of  the  daughter  nuclei.  Thus  each  new  nucleus  has, 
as  a  rule,  the  same  chromosome  composition  as  the  nucleus 
from  which  it  was  derived. 

But  the  egg  which  is  to  be  fertilized  undergoes  two 
nuclear  divisions  in  succession,  in  only  one  of  which  do  the 
chromosomes  split.  In  the  other  division  the  chromo- 
somes separate  into  two  groups  without  splitting,  and  each 
group  goes  into  a  different  cell  product.  Consequently, 


Heredity  and  Sex 


67 


in  each  of  these  products  the  number  of  chromosomes  is 
reduced  to  half  what  it  is  in  the  cells  of  the  parental  body. 
Thus  in  the  egg  of  the  mouse,  by  maturation,  the  number 
of  chromosomes  becomes  reduced  from  about  twenty-four 
to  about  twelve. 

Similar  changes  occur  in  the  developing  sperm  cell 
(Fig.  33,  upper  row).  Starting  with  the  double  or  2N 
chromosome  number,  there  are  formed  by  two  nuclear 
divisions,  with  only  one  splitting  of  chromosomes,  four 
cells,  each  with  the  reduced 
or  simplex  number  of  chro- 
mosomes, N.  From  each  of 
these  four  cells  arises  a 
tadpole-like  sperm.  Con- 
sequently, when  the  sperm 
enters  the  egg  at  fertiliza- 
tion it  brings  in  a  group 
of  N  chromosomes  (in  the 
mouse  apparently  12), 
which,  added  to  the  egg  contribution  of  N  chromosomes, 
brings  the  number  hi  the  new  organism  again  up  to  2N  (in 
the  mouse  24). 

Now,  as  regards  the  maturation  of  parthenogenetic  eggs, 
those  which  are  to  develop  without  having  been  fertilized, 
three  categories  of  cases  deserve  separate  discussion.  The 
simplest  of  these  in  many  respects  is  found  among  the 
social  hymenoptera  (ants,  bees,  and  wasps)  (see  Fig.  34, 
left  column).  The  eggs  are,  so  far  as  we  can  discover,  all 
of  a  single  type.  They  undergo  maturation  in  the  manner 
already  described,  the  chromosomes  being  reduced  to  the 
N  or  simplex  number.  The  eggs  of  most  animals,  after 
they  have  undergone  reduction,  are  incapable  of  develop- 


FIG.  33. — Top  row,  normal  spermato- 
genesis;  lower  row,  spermatogenesis  of 
simplex  male. 


68 


Heredity  and  Eugenics 


BEE          ROTIFFR       APHID 


ment  unless  fertilized,  but  those  of  the  hymenoptera  may 
develop  either  fertilized  or  unfertilized.  In  the  former 
case  a  female  is  produced,  in  the  latter  a  male.  The  simplex 
or  N  condition  is  in  this  case  the  male,  the  duplex  or  2N 

condition  is  the  female, 
naturally  the  one  of  higher 
metabolic  activity,  the  one 
which  forms  the  macro- 
gametes. 

There  is  a  peculiarity  in 
the  maturation  of  the  sperm 
cells  of  male  animals  of  this 
sort  (Fig.  33,  lower  row). 
The  cells  of  the  male  are  in 
this  case  already  in  the  re- 
duced or  simplex  condition, 
N.  In  the  production  of 
the  sperms  the  reducing 
division  is  omitted  so  far  as 
nuclear  components  are 
concerned,  so  that  each 
sperm  formed  contains  the 
full  simplex  chromosome 
number,  N.  If  it  were  less, 
the  gamete  formed  would 
perhaps  not  be  capable  of  transmitting  all  the  hereditary 
characteristics  of  an  individual. 

A  second  category  of  cases  (Fig.  34,  middle  column) 
is  represented  by  such  simple  aquatic  organisms  as  rotifers 
and  small  Crustacea,  like  Daphnia.  In  these  partheno- 
genesis occurs  exclusively  when  the  food  supply  is  very 
abundant  and  conditions  are  otherwise  favorable,  whereas 


FIG.  34. — Sex  determination  in  par- 
thenogenesis. Top  row,  nuclear  condition 
of  the  parthenogenetic  mother;  second 
row,  of  her  eggs  when  they  develop  with- 
out nuclear  reduction,  having  formed  a 
single  polar  cell;  third  row,  condition  of 
the  eggs  after  complete  maturation — the 
unfertilized  egg  in  each  case  produces  a 
male;  fourth  row,  nuclear  condition  of 
the  fertilized  egg,  always  a  female. 


Heredity  and  Sex  69 

reproduction  by  fertilized  eggs  occurs  only  when  external 
conditions,  including  food  supply,  are  not  good.  Under 
favorable  conditions  only  female  offspring  are  produced. 
The  conclusion  has  naturally  but  erroneously  been  drawn 
that  good  nutrition  in  itself  favors  the  production  of  females 
in  animals  generally,  which  is  not  true.  The  egg  produced 
by  Daphnia,  or  by  a  rotifer,  under  optimum  conditions 
does  not  undergo  reduction  (Fig.  34,  second  row).  It  remains 
in  the  2N  condition,  forming  but  a  single  polar  cell.  It  is 
therefore  unprepared  for  fertilization,  and  in  fact  it  is  not 
fertilized.  Its  sex  is  like  that  of  the  animal  which  formed 
it,  female.  Under  unfavorable  conditions,  however,  the 
eggs  of  the  rotifer  and  of  Daphnia  do  not  begin  development 
until  they  have  undergone  maturation.  They  are  also  of 
two  sizes  (Fig.  34,  third  row) — small  eggs,  which  develop 
without  fertilization  and  which  form  males,  and  large  eggs, 
which  require  fertilization,  and  which  form  females.  In 
this  category  of  cases,  as  in  that  of  the  hymenoptera,  the 
egg  which  develops  in  the  2N  condition,  either  from  failure 
of  reduction  to  occur  in  maturation  or  from  fertilization 
following  reduction,  forms  a  female;  whereas  the  egg  which 
develops  in  the  N  condition  forms  a  male. 

In  a  third  category  of  cases  there  is  a  quantitative 
difference  in  chromatin  between  male  and  female,  just  as 
in  the  foregoing  cases,  but  this  does  not  amount  to  a  whole 
set  of  chromosomes,  N,  but  to  only  a  partial  set,  one  or 
two  chromosomes  (Fig.  34,  right  column).  This  category 
of  cases  occurs  in  plant  lice  (aphids  and  phylloxerans) ; 
evidence  of  its  existence  rests  chiefly  on  recent  observations 
made  by  von  Baehr  and  Morgan.  Females  are  formed  by 
parthenogenesis  without  reduction,  occurring  under  favorable 
conditions,  just  as  in  the  case  of  rotifers.  Females  are  also 


Heredity  and  Eugenics 


formed  by  fertilization  following  reduction  under  unfavor- 
able conditions,  just  as  in  rotifers.  In  both  cases  the  female 
is  2  N.  Males  arise  only  by  parthenogenesis  under  unfavor- 
able conditions,  just  as  in  rotifers,  but  the  reduction  which 
occurs  before  development  begins  is  partial  only.  A  whole 
set,  TV,  of  chromosomes  is  not  eliminated  in  maturation,  but 
only  i  or  2  chromosomes.  Hence  the  male  condition  here 

is  2N—i  or  —2.  The  condi- 
tion of  the  gametes  formed, 
however,  is  N  in  both  sexes. 
In  spermatogenesis,  division 
of  the  germ  cells  takes  place 
into  N  and  N—  i  daughter 
cells,  but  the  latter  degene- 
rate (like  the  non-nucleated 
cells  of  the  bee  and  wasp), 
and  only  the  former  produce 
spermatozoa.  Hence  in  ferti- 
lization only  2N  zygotes  are 
produced,  which  are  invari- 
ably female. 

Summarizing  the  three 
categories  described,  we  may 
say  that  in  all  known  cases  of 
parthenogenesis,  the  female 
is  in  the  duplex  (27V)  condition,  the  male  in  the  simplex 
(TV)  or  partially  duplex  condition  (2N—i,  or  2N— 2).  The 
female  in  all  cases  has  the  greater  chromatin  content. 

In  a  great  many  insects  and  other  arthropods,  which 
are  not  parthenogenetic,  it  is  known  that,  although  the 
male,  like  the  female,  develops  only  from  a  fertilized  egg, 
nevertheless  the  male  possesses  fewer  chromosomes  than 


FIG.  35. — Diagram  of  sex  determi- 
nation when  the  female  is  homozygous, 
the  male  heterozygous. 


Heredity  and  Sex  71 

the  female.  In  such  cases  the  female  forms,  as  in  cases  of 
parthenogenesis,  only  N  gametes,  but  the  male  forms 
gametes  of  two  sorts,  N  and  N—  i  or  N— 2  (Fig.  35). 
In  consequence  zygotes  of  two  sorts  result,  those  which  are 
2N,  female,  and  those  which  are  2N—i  or  2N—2,  male. 
Thus  in  the  squash  bug,  Anasa  tristis,  according  to  Wilson, 
the  mature  egg  contains  n  chromosomes,  the  spermatozoa 
either  10  or  n  chromosomes,  the  two  sorts  being  equally 
numerous. 

Egg  n+sperm  n  produces  a  zygote  22  (2^V),  a  female 
Egg  n+sperm  10  produces  a  zygote  21  (zN-i},  a  male 

N  in  this  species  =  n;  2N=22,  the  female;  2N— 1  =  21, 
the  male.  Males  and  females  are  therefore  approximately 
equal  in  number,  as  in  most  animals  where  the  two  sexes 
are  not  subject  to  unequal  mortality.  In  the  Mendelian 
sense  the  female  is  in  such  cases  a  homozygote,  the  male  a 
heterozygote.  The  sex  of  an  individual  in  such  cases 
depends  upon  which  sort  of  a  sperm  chances  to  enter  the 

egg- 

But  the  experimental  evidence  indicates  that  both  as 
regards  sex  and  as  regards  heritable  characters  correlated 
with  sex,  these  relations  may  in  some  cases  be  reversed,  the 
female  being  heterozygous,  the  male  homozygous.  In  such 
cases  there  is  reason  to  think  that  structurally  the  male  is 
2N  but  the  female  iN-}-.  That  is,  the  female  is  still  the 
equivalent  of  the  male  plus  some  additional  element  and 
function.  A  structural  basis  in  the  chromosomes  for  such  a 
condition  has  been  described  by  Baltzer  in  the  case  of  the 
sea-urchin.  He  found  the  regular  duplex  number  of  chromo- 
somes in  the  male;  but  in  the  female,  while  the  number  was 
the  same,  one  of  the  chromosomes  was  larger  than  its  mate, 
having  an  extra  or  odd  element  attached  to  it.  In  such  a 


Heredity  and  Eugenics 


case  the  gametes  formed  by  the  male  would  all  be  N,  but 
those  formed  by  the  female  would  be  of  two  sorts  equally 
numerous,  viz.,  N  and  N-\-  (Fig.  36).  Egg  N  fertilized  by 
sperm  N  would  produce  a  zygote  2N,  a  male;  egg  N-\- 
fertilized  by  sperm  N  would  produce  a  zygote  2N-\-,  a 
female.  Hence,  here  as  in  other  animals,  the  sexes  would 

be  approximately  equal,  but 
the  sex  of  a  particular  indi- 
vidual would  depend  upon 
which  sort  of  egg  gave  rise 
to  it. 

Upon  the  existence,  as  in 
the  foregoing  cases,  of  an 
unpaired  or  odd  structural 
element  in  the  egg,  may  per- 

\  \/         /  haps  depend  the  explanation 

\          /    \      /  °f  a  curious  sort  of  heredity 

known  as  sex-limited  heredity. 
Everyone  who  knows  any- 
thing about  poultry  is  ac- 
quainted with  the  popular 
American  breed  called  barred 
Plymouth  Rock.  In  this 
breed  the  feathers  are  marked  with  alternate  bars  of  darker 
and  lighter  black.  Pure  barred  Rocks  breed  true,  but  when 
crossed  with  other  breeds,  the  male  proves  to  be  homozy- 
gous,  the  female  heterozygous  in  barring.  For  the  male 
Rock  crossed  with  a  non-barred  breed  produces  only  barred 
offspring  in  both  sexes,  but  the  female  Rock  crossed  with 
the  same  non-barred  breed  produces  offspring  approxi- 
mately half  of  which  are  barred,  the  other  half  being 
non-barred.  Further,  the  barred  individuals  in  this  cross 


FIG.  36. — Diagram  of  sex  determi- 
nation when  the  female  is  heterozy- 
gous, the  male  homozygous. 


Heredity  and  Sex  73 

are  invariably  males,  the  non-barred  ones  being  females. 
Accordingly,  the  distribution  of  barring  and  non-barring 
in  the  cross  is  sex  limited. 

The  barred  offspring  produced  by  a  cross  between 
barred  Plymouth  Rocks  and  a  non-barred  breed,  whether 
those  offspring  are  males  or  females,  prove  to  be  heterozy- 
gous in  barring,  as  we  should  expect,  the  barring  factor 
having  been  received  only  from  one  parent,  the  barred  one. 
Further,  the  non-barred  offspring  produced  by  a  barred 
Rock  female  crossed  with  a  non-barred  breed,  do  not  trans- 
mit barring,  hence  they  are  pure  recessives  as  regards 
barring.  Hence,  also,  we  are  forced  to  conclude,  as  already 
suggested,  the  female  of  the  pure  barred  Rock  breed  is 
heterozygous  as  regards  barring,  and  transmits  the  character 
only  to  her  male  offspring,  her  female  offspring  (if  the 
father  is  non-barred),  neither  being  themselves  barred  nor 
being  able  to  transmit  barring. 

A  pure  Plymouth  Rock  race  breeds  true  to  barring 
merely  because  all  its  males  are  pure,  for  the  females  are 
not  pure.  This  is  shown  by  the  following  experiment. 
If  a  heterozygous  barred  male,  produced  by  a  cross  between 
a  Rock  and  a  non-barred  breed,  is  crossed  with  barred 
females,  either  those  of  a  pure  Rock  race  or  those  produced 
by  a  cross,  the  result  is  the  same.  The  male  offspring  are 
all  barred;  the  females,  half  of  them  barred,  half  non- 
barred.  This  result  shows  that  all  barred  females  alike 
are  heterozygous  in  barring. 

Sex-limited  inheritance  such  as  this  finds  at  the  present 
time  its  most  probable  explanation  in  the  existence  in  the 
egg  of  an  extra  or  plus  element  never  found  in  the  sperm, 
this  element  pairing  with  the  sex-limited  character  in  the 
reduction  division.  Thus,  in  the  barred  Rock,  calling 


74 


Heredity  and  Eugenics 


FEMALE 


MALE 


barring  B,  the  male  of  pure  race  is  plainly  BB  and  every 
sperm  is  B.  But  the  female  clearly  contains  only  one  B 
and  cannot  be  made  to  contain  two.  Perhaps  a  second  B 
is  kept  out  by  some  structural  element,  X,  the  distinctive 
structural  element  of  the  female  individual.  Then  the 
eggs  will  be  of  two  sorts:  B  and  X  (Fig.  37).  Since  the 
sperms  are  all  5,  the  first  type  of  egg  when  fertilized  will 

contain  BB,  a  homozy- 
gous  barred  individual 
and  a  male,  since  it 
lacks  X;  the  second 
type  will  contain  BX, 
a  bird  heterozygous  in 
barring,  and  a  female, 
since  it  contains  X. 
This  agrees  with  the 
experimental  result. 

A  heterozygous 
barred  male  will  form 
two  kinds  of  sperm, 
only  one  of  which  will 
contain  B.  If  such  a 
male  be  mated  with  a  barred  female,  four  sorts  of  zygotes 
should  result  as  follows: 

Gametes  of  heterozygous  barred  male  =  B  and  — 
Gametes  of  barred  female  =B  and  X 

Zygotes =B  •  B  (homozygous  barred  male);  B  •  —(heterozygous 
barred  male),  B  •  X  (barred  female),  and  —  •  X  (non-barred  female). 

The  observed  result  of  this  cross  accords  fully  with  the 
foregoing  expectation. 

The  sex-limited  inheritance  of  barring  in  fowls  may  be 
explained,  as  we  have  just  seen,  on  the  assumption  that  the 


FIG.  37. — Diagram  of  sex-limited  inheritance 
when  the  female  is  a  heterozygote,  as  in  barred 
fowls.  X,  female  sex  determiner;  B,  barring. 


Heredity  and  Sex 


75 


MALE 


female  is  the  heterozygous  sex.  The  same  is  true  of  sex- 
limited  inheritance  in  canary  birds  and  in  the  moth,  Abraxas, 
according  to  Bateson  and  Doncaster.  But  these  relations  are 
exactly  reversed  in  the  pomace  fly,  Drosophila  ampelophila 
according  to  Morgan. 

In  Drosophila  the  female  is  apparently  homozygous  as 
regards  some  cell  structure,  X,  which  in  the  male  is  never 
represented  more  than  FEMALE 
once.  Accordingly, 

(X-RIX-R) 


the  formula  of  the 
female  is  in  such  cases 
XX;  that  of  the  male, 
X— .  Now  the  sex- 
limited  characters  in 
Drosophila  seem  to  be 
bound  up  with  the  X 
structure,  not  repelled 
by  it,  as  is  barring  in 
fowls.  Accordingly,  a 
sex -limited  character 
maybe  represented 
twice  in  the  female 
Drosophila,  but  only 
once  in  the  male;  or  in  other  words,  the  female  may  be 
homozygous  as  regards  a  sex-limited  character,  but  the 
male  can  only  be  heterozygous  (Fig.  38). 

Drosophila  normally  has  red  eyes,  but  the  redness  of 
the  eye  is  a  distinct  unit-character,  sex  limited  in  heredity. 
Further,  males  are  regularly  heterozygous  in  this  character, 
while  females  are  homozygous.  For  Morgan  has  obtained 
a  race  in  which  the  eyes  are  white,  owing  to  the  loss  of  the 
red  character;  and  reciprocal  crosses  of  this  race  with 


FIG.  38. — Diagram  of  sex-limited  inheritance 
when  the  female  is  a  homozygote,  as  in  the  red- 
eyed  Drosophila.  X,  sex  determiner;  R,  red 
eyes. 


76  Heredity  and  Eugenics 

ordinary  red-eyed  animals  yield  different  results.  The 
red-eyed  female  crossed  with  a  white-eyed  male  produces 
only  red-eyed  offspring,  but  the  red-eyed  male  crossed  with 
a  white-eyed  female  produces  offspring  only  half  of  which 
are  red  eyed,  viz.,  the  females,  whereas  the  males  are 
white  eyed. 

These  different  results  in  the  two  cases  apparently  come 
about  as  follows: 

FIRST  CASE 

Gametes  of  red-eyed  female  =  X-R  and  X-R 

Gametes  of  white-eyed  male  =  X      and  — 

Zygotes  =  X  •  X-R  (red-eyed  female),  and  —  -X-R  (red-eyed  male). 

SECOND  CASE 

Gametes  of  white-eyed  female  =X  and  X 

Gametes  of  red-eyed  male         =X-R  and  — 

Zygotes  =  X  •  X-R  (red-eyed  female),  and  —  >X  (white-eyed  male). 

A  short  condition -of  the  wings  in  Drosophila,  which 
renders  the  animal  incapable  of  flight,  is  likewise  sex 
limited  in  heredity,  as  has  been  shown  by  Morgan.  By 
crossing  two  races  of  Drosophila,  each  of  which  possessed  a 
different  sex-limited  character,  Morgan  has  been  able  to 
combine  the  two  characters  in  a  single  race.  Thus  was 
obtained  a  race  both  white  eyed  and  short  winged.  The 
synthesis  cannot  be  made  originally  in  a  male  individual, 
but  only  in  a  female.  For  only  in  the  female  can  the  two 
characters  be  brought  together,  each  associated  with  a 
different  X,  since  in  the  male  only  one  X  is  present.  Al- 
though each  sex-limited  character  seems  to  be  attached 
to  or  bound  up  with  an  X  structure,  it  evidently  has  a 
material  basis  distinct  from  X.  Otherwise  it  would  not 


Heredity  and  Sex  77 

be  possible  for  the  character  to  leave  one  X  and  attach 
itself  to  the  other,  as  apparently  takes  place  in  the  female 
when  the  combination  of  two  sex-limited  characters  in  the 
same  gamete  is  secured  through  a  cross.  The  combination 
is  apparently  secured  in  this  way: 

Gametes  uniting,  X-R  and  X— L 

Zygote  formed,  X-R  -  X-L 

Its  gametes,  X-R  and  X-L,  or  X-R-L  and  X. 

One  of  the  uniting  gametes,  X-R,  is  formed  by  the 
red-eyed,  short-winged  parent;  the  other,  X-L,  is  formed 
by  the  long-winged,  white-eyed  parent.  The  zygote  result- 
ing is  a  red-eyed  individual,  since  it  contains  R;  it  is  long 
winged,  since  it  contains  L;  it  is  a  female,  since  it  contains 
two  Xs.  Now,  its  gametes  are  of  four  sorts,  as  indicated. 
The  first  two  sorts  result  from  simple  separation  of  the 
two  Xs,  each  with  its  associated  character,  R  in  one  case, 
L  in  the  other.  But  the  third  sort  could  result  only  from 
the  attachment  of  R  and  L  to  the  same  X,  leaving  the  other 
X  without  either  R  or  L  as  the  fourth  kind  of  gamete. 
This  kind,  which  transmits  neither  red  eyes  nor  long  wings, 
would  represent  the  new  gametic  combination — white  eyed 
and  with  short  wings. 

The  experimental  evidence  that  gametes  of  these  four 
sorts  are  formed  by  females  of  the  origin  described  is  as 
follows:  When  such  a  female  is  mated  with  a  long-winged, 
white-eyed  male,  there  are  obtained  female  offspring,  all 
of  which  are  long  winged,  but  half  of  them  are  red  eyed, 
half  white  eyed.  The  male  offspring,  however,  are  of  four 
sorts,  viz.,  red  short,  white  long,  red  long,  and  white  short. 
This  result  harmonizes  with  the  hypothesis  advanced. 
For  if  the  gametes  of  the  female  are  X-R,  X-L,  X-R-L, 


78  Heredity  and  Eugenics 

and  X,  and  those  of  the  male  are  X-L  and  — ,  then  the 
following  combinations  should  result: 

X-L  •  X-R,      red  long  female 
X-L  •  X-L,      white  long  female 
X-L  •  X-R-L,  red  long  female 
X-L  •  X,         white  long  female 

•  X-R,  red  short  male 

•  X-L,   white  long  male 

•  X-R-L,  red  long  male 

•  X,  white  short  male 

This  expected  result  accords  with  that  actually  obtained 
by  Morgan. 

Color-blindness  in  man  is  a  sex-limited  character,  the 
inheritance  of  which  resembles  that  of  white  eyes  or  short 
wings  in  Drosophila,  rather  than  of  barring  in  poultry. 

Color-blindness  is  much  commoner  in  men  than  in 
women.  A  color-blind  man,  however,  does  not  transmit 
color-blindness  to  his  sons,  but  only  to  his  daughters,  the 
daughters,  however,  are  themselves  normal  provided  the 
mother  was;  yet  they  transmit  color-blindness  to  half 
their  sons.  A  color-blind  daughter  could  be  produced, 
apparently,  only  by  the  marriage  of  a  color-blind  man  with 
a  woman  who  transmitted  color-blindness,  since  the  daugh- 
ter to  be  color-blind  must  have  received  the  character  from 
both  parents,  whereas  the  color-blind  son  receives  the  charac- 
ter only  from  his  mother. 

Color-blindness  is  apparently  due  to  a  defect  in  the 
germ  cell — absence  of  something  normally  associated  there 
with  an  X-structure,  which  is  represented  twice  in  woman, 
once  in  man.  Color-blindness  follows,  therefore,  in  trans- 
mission, the  scheme  shown  in  Fig.  38. 


Heredity  and  Sex  79 

If,  as  has  been  suggested,  the  determination  of  sex  in 
general  depends  upon  the  inheritance  of  a  Mendelian  factor 
differentiating  the  sexes,  it  is  highly  improbable  that  the 
breeder  will  ever  be  able  to  control  sex.  Male  and  female 
zygotes  should  forever  continue  to  be  produced  in  approxi- 
mate equality,  and  consistent  inequality  of  male  and 
female  births  could  result  only  from  greater  mortality  on 
the  part  of  one  sort  of  zygote  than  of  the  other.  Only  in 
parthenogenesis  can  man  at  will  control  sex,  and  until  he 
can  produce  artificial  parthenogenesis  in  the  higher  animals, 
he  can  scarcely  hope  to  control  sex  in  such  animals. 

Negative  as  are  the  results  of  our  study  of  sex  control, 
they  are  perhaps  not  wholly  without  practical  value.  It  is 
something  to  know  our  limitations.  We  may  thus  save 
time  from  useless  attempts  at  controlling  what  is  uncon- 
trollable and  devote  it  to  more  profitable  employments. 


EDWARD  MURRAY  EAST 

Assistant  Professor  of  Experimental  Plant  Morphology 
Harvard  University 


CHAPTER  V 
INHERITANCE  IN  THE  HIGHER  PLANTS 

The  general  acceptance  of  the  theory  of  organic  evolu- 
tion made  necessary  a  new  botany  as  well  as  a  new  zoology. 
The  artificial  classification  of  plants  in  general  use  a  half- 
century  ago  has  been  replaced  by  one  based  upon  the  natural 
relationships  that  have  linked  together  plant  groups  during 
their  progressive  changes.  The  need  of  new  facts  in  the 
prosecution  of  this  great  work  has  played  no  small  part  in 
the  rise  of  plant  morphology,  histology,  physiology,  and 
ecology  to  well-deserved  places  of  eminence  in  science. 
But  in  so  far  as  the  valuable  subject-matter  of  these  botani- 
cal sciences  have  touched  or  been  touched  by  conceptions 
of  evolution,  they  have,  in  general,  simply  contributed 
additional  facts  which  have  harmonized  with  and  supported 
that  great  truth  already  so  well  established  by  Darwin. 

Such  a  historical  point  of  view  did  not  fully  satisfy  the 
seeker  after  knowledge.  He  wished  to  know  why  and  how 
these  things  came  about.  In  the  gratification  of  this 
curiosity  as  to  the  mechanism  of  heredity,  of  evolution,  and 
of  the  changes  that  occur  under  domestication,  rapid  prog- 
ress has  recently  been  made.  The  botanist  has  joined  hands 
with  the  zoologist  and  a  new  subdivision  of  the  biological 
sciences — Genetics — has  arisen. 

As  subject-material  for  use  in  attacking  genetic  problems, 
plants  and  animals  each  have  advantages  and  disadvan- 
tages; but  the  results  of  the  botanist  and  of  the  zoologist 
have  been  wonderfully  harmonious.  The  same  methods  are 
used  by  both,  and  the  work  of  the  pedigree  culturist,  the 

83 


84  Heredity  and  Eugenics 

histologist,  and  the  biological  chemist  supplement  each 
other  in  a  way  that  bespeaks  a  most  hopeful  future.  We 
shall  discuss  some  results  obtained  by  the  use  of  the  oldest 
method,  that  of  the  garden,  or,  to  give  it  the  more  aristo- 
cratic name,  the  pedigree  culture. 

This  method  is  old,  but  its  most  important  results  are 
modern.  A  century  and  a  half  ago  Kolreuter  carried  out 
the  first  systematic  studies  in  plant  hybridization.  Through 
them  he  was  able  to  show  that  most  reciprocal  crosses  are 
identical,  and  therefore  that  the  pollen  grain  is  as  essential 
and  important  in  determining  the  characters  of  a  hybrid 
as  is  the  ovule.  Kolreuter,  of  course,  did  not  know  the 
true  process  of  reproduction,  but  he  came  as  near  the  truth 
as  could  have  been  expected  at  the  time  by  showing  that 
an  application  of  50  or  60  pollen  grains  was  sufficient  for 
the  production  of  over  30  seeds. 

Kolreuter,  and  a  little  later  Thomas  Knight,  both  found 
that  hybrids  were  in  general  more  vigorous  than  either  of 
the  parents;  and  Knight  from  this  fact  argued  rejuvenation 
by  hybridization  and  promulgated  what  afterward  came  to 
be  known  as  the  Knight-Darwin  law.  This  was  stated  by 
Darwin  in  the  aphorism,  "Nature  abhors  perpetual  self- 
fertilization."  Our  views  on  this  subject,  as  will  be  shown 
in  the  next  chapter,  must  now  be  considerably  modified; 
nevertheless  Knight  partially  outlined  a  great  truth. 

One  other  plant  breeder  must  be  mentioned  as  markedly 
in  advance  of  his  age.  The  elder  Vilmorin  in  the  middle  of 
the  nineteenth  century  established  a  principle  which  has 
not  until  recently  been  given  the  credit  it  deserves.  Vil- 
morin insisted  that  the  only  method  of  improving  plants 
by  selection  is  to  judge  each  plant  by  the  average  condition 
of  its  progeny.  This  is  Vilmorin's  isolation  principle  and 


Inheritance  in  the  Higher  Plants  85 

is  the  direct  ancestor  of  Johannsen's  genotype  conception 
of  heredity. 

Other  items  of  fact  and  improvements  upon  technique 
were  numerous  then  as  they  are  today,  but  these  few  dis- 
coveries comprise  the  only  notable  contributions  of  the 
hybridizers  until  Abbot  Mendel's  epoch-making  researches 
on  the  pea  (Pisum  sativum)  in  the  little  cloister  garden  at 
Brunn. 

The  elements  of  Mendelianism  as  they  apply  to  animals 
have  already  been  discussed.  In  taking  up  some  of  the 
important  neo-Mendelian  facts  as  they  are  found  in  the 
higher  plants,  I  propose  to  describe  types  of  Mendelian 
inheritance  with  the  idea  of  showing  how  facts  that  are 
apparently  non-related  may  be  included  under  one  descrip- 
tive notation.  The  illustrative  material  is  drawn  largely 
from  my  own  pedigree  cultures  of  maize  or  Indian  corn 
because  they  are  naturally  more  familiar,  but  the  points 
discussed  by  no  means  apply  only  to  corn. 

It  is  of  no  small  importance  that  strict  Mendelian  nota- 
tion has  been  found  to  apply  to  the  facts  of  inheritance  in 
both  plants  and  animals.  Sex  has  arisen  separately  in  both 
kingdoms,  and  probably  even  more  than  once  in  the  vege- 
table kingdom.  It  is  therefore  a  great  argument  for  the 
universality  of  Mendelian  inheritance  in  sexual  reproduc- 
tion that  the  general  facts  are  so  similar  in  both  types  of 
organisms.  If  many  facts  in  each  kingdom  can  be  included 
in  the  Mendelian  conception  of  heredity,  the  probability 
that  it  is  a  truth  of  universal  scope  increases  by  geometrical 
progression.  Let  us  see  whether  or  not  this  is  true. 

Let  us  examine  first  a  simple  case  of  monohybridism, 
i.e.,  a  case  where  the  parents  differ  by  but  one  character. 
Such  a  character  distinguishes  sweet  corn  from  starchy  corn. 


86 


Heredity  and  Eugenics 


The  wrinkled  condition  of  the  seeds  of  sweet  corn  results 
from  an  inability  to  mature  starch  grains.  The  starchy 
corns,  as  the  name  indicates,  possess  this  feature.  One 
may  say,  therefore,  that  the  germ  cells  of  starchy  and  of 

sweet  corns  are  differ- 
entiated by  the  pres- 
ence and  the  absence, 
respectively,  of  the 
ability  to  transmit 
starchiness  (Fig.  39). 

In  the  higher  plants 
as  in  animals  the  gam- 
etes or  germ  cells  are 
simplex  in  character. 
Two  germ  cells,  one 
male  (from  the  pollen) 
and  one  female  (in  the 
ovule),  fuse  to  form  the 
duplex  cell  or  zygote 
that  develops  into  the 
plant.  The  zygote  is 
the  new  plant  genera- 
tion of  which  the  seed 
(except  the  seed  coat) 
is  but  a  resting  stage 


FIG.  39. — Segregation  of  starchiness  and 
non-starchiness  in  maize.  Above  parents  and 
FI  generation,  in  center  F3  generation,  below 
F3  generation. 


of  its  development. 
Starchiness  and  non- 
starchiness  (sweetness) 
are  seed  characters. 
One  can  see  just  what  seed  characters  the  plant  possesses, 
therefore,  as  soon  as  the  seed  is  fully  developed.  When  two 
gametes  both  carrying  the  factor  starchiness  (5)  produce  a 


Inheritance  in  the  Higher  Plants  87 

seed,  that  seed  breeds  true  to  the  character  starchiness. 
When  two  gametes  both  lacking  the  factor  starchiness 
(s)  produce  a  seed,  that  seed  breeds  true  to  the  character 
non-starchiness  or  sweetness.  The  production  of  gametes 
and  zygotes  may  be  illustrated  thus: 

Starchy  zygote  Non-starchy  zygote 


Male 
gametes 


Female          Male 
gametes     gametes 


Female 
gametes 


Starchy 
zygote 


Non-starchy 
zygote 


When  a  gamete  from  a  starchy  strain  fuses  with  a  gamete 
from  a  non-starchy  strain  a  hybrid  zygote  is  formed.  This 
zygote  is  starchy  like  the  starchy  parent  because  the 
presence  of  the  starchy  factor  from  one  parent  is  sufficient 
to  cause  the  development  of  starch.  But  the  gametes,  both 
male  and  female,  formed  by  this  hybrid  or  heterozygote,  are 
not  alike.  Half  of  them  contain  the  starchy  factor  and 
half  of  them  are  without  it.  This  being  true,  when  the  male 
and  female  gametes  of  the  hybrid  pair  indiscriminately,  the 
following  combinations  occur  in  equal  numbers: 


The  first  term  of  this  ratio,  resulting  from  the  fusion  of 
two  starchy  gametes,  is  a  starchy  zygote  that  breeds  true; 
the  second  and  third  terms,  resulting  from  the  fusion  of  a 
starchy  and  a  non-starchy  gamete,  are  again  hybrid  in 


88 


Heredity  and  Eugenics 


character;  while  the  last  term,  resulting  from  the  fusion  of 
two  non-starchy  gametes,  is  a  zygote  that  breeds  true  to 
non-starchiness.  Since  the  zygotes  having  the  gametic 
constitution  shown  by  the  first  three  terms  are  alike  in 
looks,  the  second  hybrid  generation  (F2  generation)  gives 
approximately  three  starchy  zygotes  to  one  non-starchy 
zygote.  But  the  three  starchy  zygotes,  though  alike  in 
looks,  are  different  in  their  breeding  capacity.  One  out  of 
three  breeds  true  to  starchiness;  two  out  of  three  are  hy- 
brid and  again  segregate  into  starchy  and  non-starchy  in 
the  next  generation.  Diagrammatically  the  process  may  be 
illustrated  thus: 

Starchy  gamete  Non-starchy  gamete 


s 

s 

Hybrid  zygote 


Pure 
starchy 
zygote 


Hybrid 
starchy 
zygotes 


Pure 

non-starchy 

zygote 


Inheritance  in  the  Higher  Plants  89 

In  general  one  may  say  that  when  two  individuals  are 
crossed  which  differ  from  each  other  in  paired  characters, 
of  which  one  can  usually  be  interpreted  as  the  absence  of 
the  other,  these  parental  characters  reappear  in  the  second 
hybrid  generation  unchanged  in  vigor  and  in  potency. 
The  first  hybrid  generation  may  be  exactly  like  one  parent 
in  any  particular  character,  in  which  case  that  character 
is  completely  dominant;  or,  the  hybrid  may  be  interme- 
diate between  the  two  parents  in  that  character,  in  which 
case  dominance  is  incomplete  or  absent.  Of  these  two 
phenomena  the  behavior  of  the  second  hybrid  generation 
is  by  far  the  most  important.  The  parental  characters 
are  reproduced  in  it  in  constant  ratios;  and  it  is  believed 
that  this  could  only  come  about  if  the  factors  that  represent 
these  characters  in  the  germ  cells  of  the  hybrid  occur  there 
unchanged  and  in  equal  numbers.  Generalize  this  view- 
point and  we  have  the  belief  that  organisms  behave  in 
heredity  as  if  they  were  mosaics  of  character  units,  each 
unit  being  represented  in  the  germ  cell  by  one  or  more 
factors  of  unknown  nature.  These  factors  are  commonly 
transmitted  independently  of  one  another,  and  upon  them 
depend  the  characters  of  the  individuals  to  which  they  give 
rise. 

Stated  in  fewer  words,  the  essential  feature  of  Mende- 
lianism  is  the  segregation  of  potential  characters  in  the 
gamete  in  a  state  of  apparent  purity,  and  their  recombina- 
tion by  the  law  of  chance  through  random  mating.  The 
term  "Mendelian  notation"  was  therefore  used  advisedly. 
Mendelian  notation  is  a  simple  interpretation  of  certain 
facts  of  heredity  obtained  in  pedigree  cultures.  It  is  a  con- 
venient notation  and  is  used  much  as  the  element  symbols 
are  used  in  chemistry.  It  makes  no  difference  to  analytical 


go  Heredity  and  Eugenics 

chemistry  whether  or  not  an  atom  is  a  reality,  for  the 
law  of  "Definite  and  Multiple  Proportions"  upon  which 
analytical  chemistry  is  based  is  still  valid.  In  the  same 
way,  it  makes  no  difference  whether  one  regards  unit- 
characters  as  actual  units  and  their  segregation  as  com- 
plete, or  whether  one  sees  in  organisms  a  mutual  dependence 
between  characters  and  a  quantitative  or  partial  segrega- 
tion among  gametic  factors,  the  notation  is  useful  either 
way  to  make  clear  the  facts  of  heredity  as  shown  by  actual 
experiment. 

In  a  simple  case  such  as  that  which  has  just  been  con- 
sidered (segregation  of  starchy  and  non-starchy  seeds),  the 
mathematical  reasoning  that  led  Mendel  to  his  conclusions 
can  be  shown  to  be  correct.  In  dealing  with  some  30,000 
progeny,  I  have  found  ^that  in  the  F2  generation  there 
were  23,529  starchy  and  7,811  non-starchy  seeds,  a  ratio  of 
3.0031  :  0.9969=1=  .0066.  This  is  a  3  :  i  ratio  well  within 
the  probable  error.  Furthermore,  I  find  that  the  positive 
and  negative  departures  from  the  3  :  i  ratio  that  occur  in 
individual  ears,  are  exactly  what  should  be  expected  by  the 
mathematical  theory  of  error. 

In  more  complicated  cases,  sometimes  there  are  depar- 
tures from  the  ratio  expected  normally  that  can  hardly  be 
explained  by  the  theory  of  error,  yet  hi  such  cases  one  is 
warranted  in  assuming  that  misunderstood  complications 
either  obscure  or  modify  the  action  of  Mendel's  law. 

Since  such  accurate  ratios  as  that  given  above  cannot 
be  expected  except  by  absolute  division  of  the  gametes  into 
two  kinds  equal  in  number,  it  is  difficult  to  believe  that 
there  is  not  real,  exact,  and  complete  segregation.  This 
would  be  the  inevitable  conclusion  but  for  the  fact  that 
extracted  pure  types  do  not  always  breed  true  as  they 


Inheritance  in  the  Higher  Plants  91 

should.  An  example  of  this  kind  has  arisen  in  connection 
with  the  character  under  discussion.  Among  many  thou- 
sand non-starchy  seeds  that  breed  true  after  having  been 
extracted  from  a  cross,  one  occasionally  appears  which  is 
semi-starchy  and  transmits  this  character.  What  is  the 
explanation  of  this  phenomenon?  The  aberrant  indi- 
viduals are  too  few  to  support  any  theory  of  partial  segre- 
gation yet  devised.  Is  it  not  more  logical  to  believe  that 
the  dominant  character  has  been  formed  anew  ?  It  may  be 
asked  why,  if  a  new  character  is  formed,  does  it  happen  to 
be  the  character  with  which  we  were  previously  dealing 
rather  than  some  other  character?  It  might  be  answered 
that  other  characters  do  sometimes  arise.  I  believe,  how- 
ever, that  a  more  satisfactory  answer  can  be  given.  Proto- 
plasm undoubtedly  differs  chemically  in  distinct  species, 
and  various  chemical  compounds  have  individual  tenden- 
cies toward  certain  specific  reactions.  Each  species  of 
organism  may  therefore  have  certain  paths  of  least  resist- 
ance along  which  variations  tend  to  go.  In  maize  one  path 
appears  to  lead  to  the  production  of  starch  (Fig.  40). 

Many  characters  in  the  higher  plants  have  been  shown 
to  be  inherited  as  simple  monohybrids.  Color  has  been 
a  favorite  subject  and  its  transmission  in  over  thirty  species 
has  been  more  or  less  clearly  determined.  The  list  of 
structural  characters  investigated  is  also  large.  It  includes 
such  different  things  as  tallness  and  dwarfness  (peas  and 
beans),  hairiness  and  glabrousness  (various  species),  beard- 
less and  bearded  ears  (wheat),  much-serrated  and  little- 
serrated  leaves  (nettles),  two-celled  fruit  and  many-celled 
fruit  (tomatoes).  A  criticism  has  sometimes  been  raised 
that  most  of  these  characters  are  morphologically  unim- 
portant. In  a  measure  this  criticism  is  valid,  yet  there  is 


92  Heredity  and  Eugenics 

a  good  reason  for  its  truth.  The  mechanism  of  the  heredi- 
tary transmission  of  any  character  can  only  be  demon- 
strated when  two  "crossable"  varieties  differ  in  this 
character.  The  characters  most  important  to  a  species  are 


FIG.  40. — Starchiness    in    an    extracted    recessive.     On  either  side  normal 
segregates,  in  center  semi-starchy  ear  grown  from  non-starchy  seed. 

characteristic  of  the  species.  No  individual  is  without 
them;  and  this  being  true,  the  method  of  their  inheritance 
must  remain  unknown.  It  is  often  impossible  even  to  tell 
whether  there  is  a  single  or  a  complex  set  of  factors  con- 


Inheritance  in  the  Higher  Plants  93 

cerned  in  the  hereditary  transmission  of  a  character.  Com- 
plexity shows  only  when  the  two  parents  differ  in  several 
factors  involving  the  same  character.  If  they  differ  by 
only  one  factor,  inheritance  may  appear  to  be  very  simple; 
but  crosses  between  other  individuals  similar  to  the  former 
in  appearance  may  show  an  entirely  different  state  of  affairs. 
A  very  good  illustration  of  what  is  meant  by  this  statement 
is  the  inheritance  of  the  purple  color  of  maize  that  occurs 
in  the  single  layer  of  cells  immediately  beneath  the  hull  or 
pericarp — the  aleurone  cells  (Fig.  41).  When  an  individual 
of  a  variety  containing  the  purple  color  is  crossed  with 
certain  white  varieties,  the  hybrid  is  purple,  showing  dom- 
inance of  the  purple  character.  The  second  hybrid  genera- 
tion produces  three  purple  seeds  to  one  white  seed.  Since 
this  is  the  normal  monohybrid  ratio,  one  would  suppose 
that  the  character  in  question  is  simple.  This  is  only 
apparently  the  case,  however,  for  when  the  same  purple 
variety  is  crossed  with  other  white  varieties  the  ratio  of 
purple  to  white  seeds  is  such  that  one  knows  the  varieties 
must  have  differed  by  two  gametic  factors  affecting  the 
development  of  the  purple  character,  instead  of  one.  In 
order  that  this  matter  may  be  made  clear,  the  dihybrid 
ratio  must  be  explained. 

The  dihybrid  ratio  is  that  obtained  when  the  parents 
differ  by  two  character  pairs.  It  is  the  algebraic  product 
of  two  (3+1)  ratios.  The  chances  are  iXi=yV  that  the 
two  dominant  or  presence  characters  occur  together,  f  Xi  = 
-^  that  the  dominant  character  of  the  first  pair  meets  the 
recessive  or  absence  character  of  the  second  pair,  jXf =TV 
that  the  recessive  character  of  the  first  pair  meets  the 
dominant  character  of  the  second  pair,  and  iXi=TV  that 
both  the  recessive  characters  occur  together.  If  we  let  the 


94 


Heredity  and  Eugenics 


two  pairs  of  characters  be  represented  by  A  and  a  and  B 
and  b  the  ratio  of  the  occurrence  of  types  in  the  F2  gener- 
ation is  AA-\-2  Aa-\-aa  and  BB-\-2Bb+bb  when  considered 


FIG.  41. — Inheritance  of  purple  aleurone  cells.  Ear  i  a  pure  extracted 
purple,  ear  2  monohybrid  with  3  to  i  ratio,  ear  3  dihybrid  with  9  to  7  ratio,  ear  4 
a  pure  extracted  white. 

separately.  If  one  wishes  to  obtain  the  probable  ratio 
when  both  characters  are  considered  together  he  has  but 
to  multiply  the  two  series  together.  This  gives  the  prod- 
uct AABB+AAbb+aaBB+aabb+2AABb  +  2aaBb+ 


Inheritance  in  the  Higher  Plants 


95 


bb-\-2AaBB-\~4AaBb.  Since  heterozygotes  resemble  homo- 
zygotes  in  appearance  in  the  cases  of  complete  dominance, 
however,  the  visible  appearance  of  the  F2  generation  is 
gAB  :  $Ab  :  ^aB  :  lab. 

Perhaps  the  easiest  method  of  showing  the  combinations 
of  gametes  in  Mendelian  inheritance  is  by  the  use  of  four 
squares  multiplied  once  by  four  for  each  character  pair. 
In  the  case  of  dihybrids  sixteen  squares  are  necessary. 
Write  each  possible  gametic  combination  of  the  male  cells 
in  each  horizontal  row  of  squares,  AB,  Ab,  aB,  and  ab. 
Next  write  the  same  combinations  for  the  female  gametes 
in  each  vertical  column  of  squares.  This  gives  all  the 
zygotic  combinations  possible. 

We  are  now  ready  to  see  just  why  one  cannot  tell  whether 
he  is  dealing  with  a  simple  or  complex  state  of  affairs  in 
Mendelian  inheritance.  In  the  monohybrid  ratio  of  purple 
and  non-purple  aleurone  cells  of  maize  the  segregation  in  the 
F2  generation  is: 


p 

p 

p 

p 

p 

p 

p 

p 

Three  purples  to  one  non-purple  are  produced. 

In  the  dihybrid  ratio  when  other  white  varieties  were 
used  as  one  of  the  parents,  nine  purples  to  seven  non-purples 
were  produced.  This  simply  means  that  two  factors  are 
necessary  to  produce  the  purple  color.  These  factors  may 


Heredity  and  Eugenics 


be  represented  by  the  letters  C  and  P.  The  gametic  formula 
of  the  purple  variety  is  CP;  the  gametic  formula  of  these 
particular  white  varieties  is  cp.  If  either  C  or  P  is  absent 
from  the  zygotic  formula  of  F2  then  the  zygote  is  white  as 
is  shown  in  the  diagram. 

DIAGRAM  ILLUSTRATING  INHERITANCE  OF  PURPLE  ALEURONE 
CELLS  IN  MAIZE  WHEN  TWO  FACTORS  ARE  CONCERNED 


CP 

CP 

CP 

CP 

CP 

cp 

cP 

cp 

Purple 

Purple 

Purple 

Purple 

Cp 

Cp 

Cp 

cp 

CP 

Cp 

cP 

cp 

Purple 

White 

Purple 

White 

cP 

cP 

cP 

cP 

CP 

cp 

cP 

cp 

Purple 

Purple 

White 

White 

cp 

cp 

cp 

cp 

CP 

cp 

cP 

cp 

Purple 

White 

White 

White 

The  formula  of  the  purple  is  therefore  CCPP,  but  whites 
with  formulas  CCpp,  ccPP,  and  ccpp  may  exist.  When  the 
whites  have  formulae  CCpp  or  ccPP  they  give  monohybrid 
ratios  when  crossed  with  the  purple,  but  when  they  have 
the  formula  ccpp  a  dihybrid  results. 

This  illustration  shows  both  why  one  cannot  tell  just 
how  complex  a  character  is,  and  why  characters  essential 
to  the  species  cannot  be  analyzed. 

These  cases  of  Mendelian  inheritance  are  types.     Other 


Inheritance  in  the  Higher  Plants  97 

cases  may  be  more  complex  in  appearance  but  this  is  a  sur- 
face complexity  only.  They  yield  to  similar  analyses  when 
they  are  properly  understood.  This  complexity  in  appear- 
ance has  many  tunes  made  cases  appear  to  be  exceptions 
to  Mendel's  general  law.  Various  ratios  have  been  obtained 
that  were  seemingly  inexplicable,  but  these  one  by  one  have 
been  found  to  be  merely  variations  of  the  simple  ratios  that 
we  have  just  discussed.  Perhaps  the  most  interesting  of 
these  aberrant  ratios  are  those  cases  of  heredity  dealing 
with  latent  characters.  We  will  consider  some  of  these 
briefly  as  examples  of  the  various  manifestations  which  are 
found  in  the  hereditary  transmission  of  plant  characters. 

One  of  the  most  important  classes  of  latency  we  have  just 
discussed.  It  is  called  latency  of  separation.  Where  a 
character  exists  through  the  interaction  of  two  factors, 
these  factors  may  at  some  time  become  separated,  that  is, 
possessed  by  different  individuals.  When  this  occurs  the 
character  is  apparently  lost  and  does  not  again  appear 
unless  two  individuals  bearing  the  complementary  factors 
are  crossed.  This  is  the  explanation  of  the  old  phenome- 
non of  reversion  after  crossing.  It  was  first  explained  by 
Bateson  from  experiments  with  sweet  peas.  He  found  that 
two  white  varieties  yielded  the  purple  color  of  the  wild 
sweet  pea  when  crossed.  In  the  same  way  I  have  found 
that  the  white  seeds  in  the  dihybrid  ratio  of  9  :  7,  shown 
by  the  purple  X  non-purple  cross  of  maize  varieties,  give 
purple  seeds  when  crossed  at  random.  The  non-purples 
exist  in  the  following  ratios: 


98 


Heredity  and  Eugenics 


When  crossed  at  random,  there  are  7X6  =  42  possible  com- 
binations of  which  24  give  all  white  seeds  and  18  give  some 
purple  seeds.  Of  these  18  ears  there  would  be  on  the  aver- 
age 2  pure  purples,  8  with  purples  and  whites  in  a  ratio  of 
i  :  i,  and  8  with  purples  and  whites  in  a  ratio  of  i  :  3.  Such 
results  have  been  obtained  experimentally  and  examples 
are  shown  in  Fig.  42. 


FIG.  42. — Reversion  due  to  latency  of  separation.  Purple  seeds  produced  by 
crossing  whites.  Ear  i,  i  to  3  ratio;  ear  2,  i  to  i  ratio. 

A  different  kind  of  latency  is  simply  invisibility  of  a 
character  due  to  some  obscuring  factor  which  may  be 
removed  by  means  of  a  cross  in  which  the  latter  is  absent. 
This  latency  is  called  that  of  hypostasis,  a  hypostatic  char- 
acter being  one  which  is  obscured  by  another  called  the 
epistatic  character.  There  are  instances  where  this  epi- 
static  character  may  be  removed  mechanically  and  the 
hypostatic  character  revealed.  Such  a  one  is  the  red-eared 
maize,  for  the  color  there  lies  in  the  hull  or  pericarp.  This 


Inheritance  in  the  Higher  Plants  99 

may  be  scraped  off  to  show  the  color  of  the  true  seed 
which  may  be  either  yellow  or  white.  In  most  cases, 
however,  the  relations  are  physiological  and  the  hypostatic 
character  can  be  demonstrated  only  by  crossing.  For 
example,  the  maize  with  purple  aleurone  cells  carries  also 
a  factor  for  red  aleurone  cells  which  can  be  demonstrated 
only  by  crossing  it  with  a  variety  in  which  the  purple  factor 
is  absent.  There  is  produced  an  F2  generation  with  a  ratio 
of  27  purples  :  9  reds  :  28  whites. 

This  statement  may  appear  to  be  a  direct  contradiction 
of  the  interpretation  of  the  inheritance  of  purple  aleurone 
color  that  has  just  been  given.  In  reality  it  is  merely 
another  illustration  of  the  fact  that  one  can  never  know 
definitely  the  factors  involved  in  producing  a  character,  for 
he  can  never  feel  assured  that  the  parents  involved  in  the 
cross  have  differed  in  all  the  factors  that  affect  its  develop- 
ment. When  the  purple  was  crossed  with  the  white  and  a 
ratio  of  9  purples  :  7  whites  obtained  in  the  F2  generation, 
it  was  proper  to  interpret  the  purple  parent  as  P  P  C  C 
and  the  non-purple  parent  as  p  p  c  c.  But  when  the  purple 
is  crossed  with  another  non-purple  and  a  ratio  of  27  purples : 
9  reds  :  28  whites  is  obtained  in  the  F2  generation,  it  is  clear 
that  a  different  interpretation  is  necessary.  The  purple 
parent  has  the  formula  P  P  R  R  C  C  and  the  white  parent 
the  formula  p  p  r  r  c  c.  The  zygotic  formula  of  a  pure  red 
seed  is  R  R  C  C  and  of  a  pure  purple  seed  is  P  P  R  R  C  C, 
but  a  seed  with  the  formula  P  P  C  C  is  white.  In  other 
words,  the  factor  P  produces  the  visible  purple  color  only 
in  the  presence  of  factors  C  and  R.  The  purple  has  always 
the  constitution  P  P  R  R  C  C  ;  when  it  is  crossed  with  whites 
having  the  characters  P  P  RRcc  or  P  P  r  r  C  C  ,  a  ratio 
of  3  purples  :  i  white  is  obtained  in  F2;  when  it  is  crossed 


ioo  Heredity  and  Eugenics 

with  a  white  having  the  composition  P  P  r  r  c  c,  a  ratio  of 
9  purples  :  7  whites  is  obtained  in  F2;  when  it  is  crossed 
with  a  white  having  the  composition  pprrcc,  a  ratio  of  27 
purples  :  9  reds  :  28  whites  is  obtained  in  F2. 

It  is  possible  that  another  factorial  difference  may  yet 
be  found  which  will  show  this  character  to  be  still  more 
complex.  Baur,  Bateson,  Saunders,  and  Gregory  have 
shown  that  the  sap  colors  of  the  flowers  of  Antirrhinum,  of 
Lathyrus,  of  Matthiola,  and  of  Primula  belong  to  this  type 
and  are  yet  more  complex.  But  this  does  not  affect  our 
general  conception  of  the  inheritance  of  the  colors  in  the 
least. 

Sometimes  latent  characters  very  similar  to  this  are  due 
to  the  presence  of  a  second  inherited  factor  which  does  not 
allow  the  first  character  to  develop.  This  is  called  latency 
due  to  inhibition.  Similarly  there  may  be  inherited  char- 
acters which  help  to  a  more  perfect  development  other 
independently  transmitted  characters.  This  is  undoubtedly 
an  important  phase  of  Mendelianism  for  although  we  may 
conceive  factors  as  holding  within  themselves  the  poten- 
tialities of  certain  characters,  they  undoubtedly  are  influ- 
enced in  their  development  by  the  development  of  other 
inherited  characters.  One  may  imagine  that  factors  repre- 
senting characters  may  be  transmitted  but  are  either  not 
expressed  at  all  or  are  developed  to  a  limited  degree  owing 
to  the  presence  or  the  absence  of  other  inherited  characters 
that  affect  this  development. 

Perhaps  this  theoretical  conception  may  be  made  plain 
by  an  example  of  what  has  been  termed  latency  of  fluctua- 
tion. In  this  class  are  included  characters  which  are  poten- 
tially present  in  an  organism  but  which  may  develop  to  a 
greater  or  less  extent  due  to  varying  influences  which  sur- 


Inheritance  in  the  Higher  Plants  101 

round  them.  There  is  a  red  color  in  the  pericarp  or  hull  of 
the  maize  seed  which  is  transmitted  as  a  simple  Mendelian 
monohybrid  when  crossed  with  a  variety  in  which  the 
character  is  absent,  but  the  color  develops  to  its  full  extent 
only  in  bright  sunlight.  When  a  black  bag  is  placed  over 
the  young  ear  the  color  does  not  develop  at  all,  yet  such  a 
colorless  ear  will  transmit  the  color  as  well  as  if  that  ear  had 
developed  in  bright  sunlight.  One  may  easily  see  then 
how  he  might  be  deceived  in  the  classification  of  such  indi- 
viduals and  thereby  draw  wrong  conclusions  regarding  the 
inheritance  of  the  character. 

Though  the  example  just  given  is  one  of  latency  of  fluc- 
tuation, it  really  consists  hi  the  character  being  partially 
inhibited  by  absence  of  light.  One  may  see  from  it,  how- 
ever, that  there  can  be  real  latency  of  inhibition  through  the 
influence  of  inherited  factors  that  affect  the  development  of 
independent  characters. 

We  have  hitherto  considered  characters  that  seem  to  be 
transmitted  independently  of  one  another.  Let  us  now 
spend  a  moment  in  discussing  characters  that  appear  to  be 
either  coupled  or  antagonistic  to  each  other  in  their  trans- 
mission. Some  very  interesting  results  on  this  subject 
have  been  obtained  by  Emerson  (Fig.  43).  There  are 
maize  varieties  which  are  red  in  both  the  pericarp  of  the 
seed  and  the  cob.  When  one  of  these  is  crossed  with  a 
variety  in  which  color  is  absent  in  both  the  pericarp  and 
cob,  the  second  hybrid  generation  produces  three  ears  like 
the  colored  parent  to  one  ear  like  the  white  parent.  One 
might  suppose  that  the  color  in  pericarp  and  in  cob  was  due 
to  a  single  gametic  factor.  This  can  hardly  be  the  case,  how- 
ever, for  there  are  varieties  with  red  pericarp  and  white  cob 
and  varieties  with  white  pericarp  and  red  cob.  When  two 


102 


Heredity  and  Eugenics 


such  varieties  are  crossed  together  the  first  hybrid  genera- 
tion produces  ears  with  red  pericarp  and  red  cob  like 
the  colored  variety  in  the  previous  cross.  In  the  second 
hybrid  generation,  however,  we  find  produced  i  red 


FIG.  43. — Red  pericarp  and  red  cob  coupled  in  inheritance.  (Photo  by 
Emerson.)  F2  generation  shown.  Ears  i,  2,  3  with  red  cob  and  red  pericarp, 
ear  4  with  white  cob  and  white  pericarp. 

pericarp  with  white  cob:  2  red  pericarp  with  red  cob:  i 
white  pericarp  with  red  cob.  The  first  and  third  classes 
breed  true  to  their  conditions,  but  the  second  class  proves 
to  be  always  heterozygous  and  breaks  up  in  the  next  gen- 
eration as  did  those  with  similar  characters  of  the  first 
hybrid  generation. 


Inheritance  in  the  Higher  Plants 


103 


Without  going  into  the  theory  of  this  phenomenon  it  is 
apparent  that  in  the  first  case  red  pericarp  and  red  cob 


FIG.  44. — -Red  cob  and  red  pericarp  antagonistic  in  inheritance.  (Photo 
by  Emerson.)  F2  generation  shown.  Ears  i  and  4,  like  parents,  are  pure  types. 
Ears  2  and  3  are  heterozygous. 

were  not  produced  by  a  single  factor  in  the  usual  sense,  but 
by  two  individual  factors  coupled  in  their  inheritance.  In 
the  second  cross  the  two  factors  were  not  coupled;  in  fact 


iO4  Heredity  and  Eugenics 

they  were  just  the  opposite,  they  were  antagonistic  to  each 
other  so  that  no  pure  types  were  produced  having  red  peri- 
carps and  red  cobs  (Fig.  44).  This  is  an  example  of  a  fea- 
ture which  is  probably  very  widespread  in  the  plant  world, 
but  of  which  we  at  present  know  little.  It  is  cited  for  two 
reasons;  first,  to  show  that  characters  may  at  one  time  be 
antagonistic  to  each  other  and  at  another  time  coupled 
together,  and  second,  to  show  that  one  is  not  able  to  say 
beforehand  whether  a  manifestation  of  a  character  hi 
several  organs  is  due  to  one  or  to  several  separately 
inherited  factors. 

Leaving  out  of  consideration  sex-limited  inheritance  of 
which  little  is  known  in  plants,  we  have  now  briefly  gone 
over  simple  type  cases  of  some  of  the  most  important  present- 
day  Mendelian  knowledge;  but  we  have  considered  only 
crosses  in  which  the  potential  character  or  characters  are 
present  in  one  parent  and  absent  in  the  other.  At  least 
they  behave  that  way  and  may  reasonably  be  so  interpreted. 
Such  differences  between  parents  are  qualitative,  but  most 
differences  between  parents  are  quantitative  and  give  an 
apparent  blend  in  the  first  hybrid  generation.  Nearly  all 
cases  where  varieties  differ  in  the  size  of  their  organs  are 
of  this  kind.  Can  such  phenomena  be  interpreted  by 
Mendelian  notation  ?  I  believe  they  can.  One  may  think 
of  a  factor  for  a  character  being  present  in  the  germ  cell 
not  only  once  but  twice  or  even  a  greater  number  of  times. 
If  these  factors  are  transmitted  independently  and  are  not 
paired  with  each  other,  but  each  with  its  own  absence,  one 
may  very  easily  interpret  size  inheritance.  For  example, 
when  a  certain  dent  variety  of  maize  is  crossed  with  a  flint 
variety  as  shown  in  Fig.  45,  an  intermediate  condition  is 
obtained  in  the  first  hybrid  generation.  In  the  second 


Inheritance  in  the  Higher  Plants  105 

hybrid  generation  one  ear  like  each  original  parent  is 
obtained  out  of  every  sixteen  instead  of  every  four  (Figs. 
46,  47).  This  inheritance  is  therefore  dihybrid  in  charac- 
ter. In  like  manner,  a  higher  number  of  transmissible  fac- 
tors may  affect  the  development  of  what  is  to  the  eye  a 
single  character. 

Since  dominance  is  not  an  essential  feature  of  Mendeli- 
anism,  size  characters  may  show  intermediates  or  blends 
in  the  first  hybrid  generation  and  still  fulfil  the  essential 
conditions  of  Mendel's  law  by  recombining  in  such  a  fashion 
as  to  produce  individuals  like  either  parent  in  the  second 
hybrid  generation  provided  a  sufficiently  large  number  of 
individuals  to  allow  for  the  recombination  of  several  factors 
is  grown  in  that  generation.  Such  recombinations  do  occur 
and  can  be  shown  by  experiment.  For  example,  the  small 
variety  of  corn,  Tom  Thumb,  when  crossed  with  a  larger 
variety  like  the  Black  Mexican  (Fig.  48),  gives  a  first  hybrid 
generation  that  is  intermediate  between  the  two  parents. 
One  may  call  this  a  blended  condition;  yet  if  there  were 
blended  inheritance  this  condition  would  be  transmitted, 
while  if  Mendelian  recombination  occurred,  sizes  compa- 
rable to  either  parent  would  be  obtained  in  the  second  hybrid 
generation.  Such  extremes  were  obtained  as  is  shown  in 
the  figure. 

If  the  possible  Mendelian  interpretation  of  quantitative 
characters  has  been  made  clear,  the  statement  that  Men- 
del's law  is  probably  universally  applicable  where  sexual 
reproduction  occurs  will  not  seem  rash.  There  are  still 
some  apparent  exceptions  to  the  law,  but  they  are  so  few 
that  one  may  well  believe  we  simply  do  not  know  how  to 
bring  them  into  line  and  not  that  they  are  actual  exceptions. 
Of  course  it  is  quite  likely  that  there  are  other  laws  which 


io6  Heredity  and  Eugenics 

modify  the  action  of  Mendel's  law  in  a  manner  similar  to 
that  in  which  the  physical  laws  holding  good  under  theo- 
retical conditions  are  modified  under  conditions  existing 
in  nature. 

Granted,  then,  that  Mendelianism  is  broad  in  scope, 
could  it  have  been  of  great  value  during  the  progress  of 


FIG.  45. — Inheritance  of  physical  condition  of  endosperm  in  maize.     Parents 
and  Fi  generation  shown. 

evolution?  That  it  should  have  been  of  great  value  to 
very  primitive  forms  of  life  does  not  seem  possible,  and  even 
after  the  origin  of  sex  its  precise  importance  is  somewhat 
problematical.  It  has  disposed  of  one  of  the  main  criticisms 
against  Darwin,  at  least,  that  of  the  swamping  effects  of 
intercrossing  upon  newly  arisen  characters  that  are  an  advan- 
tage to  the  species.  Since  characters  are  segregated  as  units 


Inheritance  in  the  Higher  Plants 


107 


FIG.  46. — Inheritance  of  physical  condition  of  endosperm  in  maize.    Flint- 
like  F2  segregate  above  and  F3  progeny  below. 


FIG.  47. — Inheritance  of  physical  condition  of  endosperm  in  maize.     Dent- 
like  F2  segregate  above  and  F3  progeny  below. 


io8  Heredity  and  Eugenics 

in  the  hybrid  it  matters  not  whether  they  are  dominant 
or  recessive  or  whether  there  is  no  dominance,  there  will 
be  no  dilution  from  intercrossing.  A  second  and  more 
important  advantage,  due  to  the  operation  of  the  law, 
results  from  the  recombination  of  characters.  Characters 
may  be  transmitted  as  units  and  chance  recombinations 
of  these  characters  may  occur  without  anything  really  new 
to  the  organism  being  formed,  yet  hi  this  recombination 
the  organism  as  a  whole  may  be  better  fitted  for  its  environ- 
ment than  ever  before.  And  this  is  giving  recombination 
its  smallest  value,  for,  however  independently  potential 
characters  may  be  transmitted,  no  one  believes  that  a 
developing  organism  is  simply  a  mass  of  independently 
developing  unit-characters.  The  characters  of  an  organ- 
ism are  more  or  less  dependent  upon  one  another  in  their 
expression,  and  in  this  interdependent  development  the 
greatest  possibility  for  good  recombinations  occurs.  Theo- 
retically nothing  new  may  result  from  the  mere  act  of  cross- 
ing, but  practically  a  new  combination  of  old  characters 
may  result  in  something  quite  different.  A  little  thought 
and  the  use  of  chemical  analogies  where  the  same  mixtures 
produce  different  chemical  results  under  different  physical 
conditions,  show  the  importance  of  this  conception  to  Men- 
delian  theory.  Yet  it  is  not  necessary  to  believe  the  cur- 
rent teaching  that  one  has  only  new  recombinations  and 
not  new  characters  to  deal  with  in  crosses.  The  theory 
that  several  germ-cell  factors  may  be  due  to  produce  the 
same  character  gives  us  a  reasonable  and  orthodox  explana- 
tion of  the  origin  of  characters  really  and  truly  new  by  the 
interaction  of  gametic  factors  that  are  old.  For  example, 
let  us  suppose  that  in  a  certain  species  with  a  petioled  leaf 
there  is  a  variety  which  has  the  presence  of  factor  A  pro- 


Inheritance  in  the  Higher  Plants 


109 


a  t  a  i 


>r>ftf>  S  6  7 

YUK  4-  11 


IS        /6        /7 

ff,.Y*r      3        rr        )i       rs       26       /r      10        72 


Unjth      7  8          »          10          11         12  13          14          15          16        17 


FIG.  48. — Inheritance  of  length  of  ear  in  maize.  Parents  above,  FI  genera- 
tion in  center,  F2  generation  below.  Class  sizes  in  centimeters  with  number  of 
variates  below. 


no  Heredity  and  Eugenics 

ducing  a  slight  tendency  toward  a  sessile  leaf.  Factors  B 
and  C  may  ultimately  arise  as  modifications  of  factor  A. 
Each  alone  may  produce  the  same  result  as  A;  yet  if  they 
are  transmitted  independently,  are  not  allelomorphic  to 
each  other  and  are  cumulative  in  their  action,  a  sessile  leaf — 
a  new  character — is  produced. 

The  remainder  of  this  chapter  will  be  devoted  to  a  con- 
sideration of  Johannsen's  genotype  conception  of  heredity. 
It  may  seem  as  if  Mendelism  has  been  dropped  abruptly  to 
take  up  a  new  subject.  This  is  not  the  case.  The  genotype 
conception  of  heredity  is  merely  an  acknowledgment  of  the 
universality  of  Mendelism. 

Johannsen,  who  developed  the  genotype  idea,  found 
that  some  variations  were  not  inherited.  These  were  the 
general  variations  in  relative  perfection  of  development  of 
parts,  caused  by  varying  physical  and  chemical  conditions 
of  environment.  This  is  only  an  acceptance  of  Weismann's 
theory  that  inheritance  is  from  germ  cell  to  germ  cell,  and 
that  ordinary  environmental  influences  affecting  the  body 
only  are  not  transmissible.  Of  course  both  Weismann  and 
Johannsen  acknowledge  that  certain  changes  in  environ- 
ment may  produce  structural  modification  of  the  germ 
plasm  and  therefore  a  heritable  variation,  but  whether  the 
heritable  variation  produced  is  ever  identical  with  the 
adaptive  response  of  the  parent  organism  is  still  in  dispute. 

If  this  contention  be  true,  it  follows  that  the  hereditary 
characters  of  an  organism  are  determined  by  the  consti- 
tution of  the  fertilized  egg  from  which  it  came.  Johannsen 
denotes  the  sum  total  of  the  gametic  factors  making  up  a 
zygote  by  the  word  genotype.  If  two  individuals  possess 
identical  gametic  factors,  they  are  members  of  the  same 
genotype.  Of  course  no  one  can  describe  a  genotype  in 


Inheritance  in  the  Higher  Plants  in 

concrete  terms.  It  is  a  theoretical,  a  philosophical,  concep- 
tion. If  one  crosses  two  individuals,  the  genes  or  gametic 
factors  common  to  each  breed  true.  He  can  obtain  an 
idea  of  the  behavior  in  heredity  of  those  factors  only  which 
are  not  common  to  the  two  parents.  These  factors  segre- 
gate and  recombine  in  definite  proportions.  They  follow 
Mendel's  law.  The  genotype  conception  of  heredity  is 
therefore  the  conception  that  duplex  or  homozygous  gametic 
factors  are  due  to  produce  identical  results  within  the 
limits  of  variability  imposed  by  external  conditions  and 
by  the  influence  of  other  independent  gametic  factors  during 
ontogeny,  no  matter  what  is  the  appearance  of  the  indi- 
vidual from  which  they  were  derived.  This  is  a  strict 
Mendelian  conception  of  heredity  extended  to  the  organism 
as  a  whole. 

We  need  not  go  into  the  many  lines  of  work  that  support 
the  genotype  theory.  Considered  in  a  broad  way  I  believe 
no  reputable  modern  work  is  irreconcilable  to  it,  although 
some  authors  do  not  so  interpret  their  work.  All  modern 
plant  breeding  is  in  its  support,  for  the  principle  of  Vilmorin, 
the  progeny  test,  which  is  the  basis  of  all  modern  selection 
work,  is  founded  upon  the  same  conception.  In  naturally 
inbred  plants,  one  has  commercial  strains  which  are  mechani- 
cal mixtures  of  near-homozygotes,  and  can  be  immediately 
isolated.  In  naturally  cross-bred  plants  or  in  bisexual  ani- 
mals, one  has  physiological  mixtures,  that  is,  hybrids  or 
heterozygotes,  from  which  it  takes  somewhat  longer  to  iso- 
late particular  strains  that  are  genotypically  homozygous  in 
respect  to  certain  characters,  but  in  which  the  separation 
is  accomplished  by  the  same  means — the  breeding  test. 

In  the  theoretical  homozygous  genotype  transmissible 
variations  may  occur,  for  no  one  believes  protoplasm 


ii2  Heredity  and  Eugenics 

unchanging.  Such  a  conception  would  be  mechanical  and 
not  biological.  These  changes  must  affect  the  germ  cell 
structurally  to  be  inherited.  They  may  be  large,  they  may 
be  small.  We  may  call  them  mutations  with  DeVries,  or 
we  may  use  the  simpler  and  broader  term,  inherited  varia- 
tions. When  they  occur,  new  varieties  may  be  isolated 
in  which  they  are  present,  and  these  may  be  considered 
to  be  relatively  permanent  as  compared  with  the  non- 
inherited  fluctuations  that  continually  occur  due  to  varying 
environment. 

One  may  question  the  stability  of  unit-characters  as  does 
Castle,  but  I  cannot  see  how  this  affects  the  truth  of  the 
genotype  conception  as  a  help  toward  an  idea  of  the  process 
of  heredity.  Stability  is  a  relative  thing.  Why  is  there  not 
a  scale  of  stability  in  biology  even  as  in  chemistry  ?  Many 
unit-characters  are  high  in  the  scale  of  stability,  others  may 
be  low.  Certain  characters  ordinarily  transmitted  perfectly 
may  possibly  be  modifiable  by  selection.  We  might  imagine 
their  factors  to  be  huge  chemical  molecules,  stable  as  a  whole 
but  modifiable  by  isomerism  or  even  the  dropping  off  or 
adding  on  of  unimportant  radicles.  This  is  a  smaller  issue, 
unimportant  when  compared  with  the  genotype  conception 
as  a  whole.  The  important  point  as  the  foundation  of  the 
modern  view  of  heredity  I  give  in  Johannsen's  own  words: 
"Personal  qualities  are  the  reactions  of  the  gametes  joining 
to  form  a  zygote;  but  the  nature  of  the  gametes  is  not  deter- 
mined by  the  personal  qualities  of  the  parents  or  ancestors 
in  question." 


CHAPTER  VI 

THE  APPLICATION  OF  BIOLOGICAL  PRINCIPLES  TO 
PLANT  BREEDING 

In  this  chapter  I  shall  take  up  the  commercial  appli- 
cation of  some  of  the  principles  of  plant  genetics  previously 
discussed. 

The  fact  must  again  be  emphasized  that  there  are  two 
kinds  of  variation: 

1.  Fluctuating  variations,  which  are  due  solely  to  sur- 
rounding influences  such  as  better  position  for  develop- 
ment or  varying  fertility  of  the  soil.     Such  variations  are 
not  inherited. 

2.  Inherited  variations,  which  are  due  to  some  structural 
change  in  the  reproductive  cells.    These  variations  may 
depend  upon  environmental  conditions  for  their  full  devel- 
opment but  not  for  their  transmission. 

Inherited  variations  possess  the  only  value  to  the  plant 
breeder,  yet  the  work  of  improving  plants  is  rendered  a 
great  deal  more  irksome  by  the  presence  of  fluctuations  and 
by  the  fact  that  one  cannot  tell  the  gametic  constitution  of 
a  plant,  that  is,  its  breeding  capacity,  by  its  appearance. 
The  whole  problem  of  the  plant  breeder  is  to  find,  to  fix,  and 
to  recombine  desirable  inherited  variations,  and  to  do  this 
in  spite  of  their  tendency  to  be  obscured  by  fluctuations. 
The  methods  used  to  accomplish  these  results  will  be  taken 
up  presently.  First,  attention  must  be  called  to  a  physio- 
logical phenomenon  that  may  be  made  a  tool  of  such  high 
value  to  the  plant  breeder  that  the  statement  just  made 
concerning  his  problem  is  apparently  untrue.  This  matter 

"3 


ii4  Heredity  and  Eugenics 

is  an  exception,  however — a  thing  apart  from  the  usual 
breeding  procedure. 

It  will  be  remembered  that  when  a  plant  receives  iden- 
tical character  factors  from  each  parent,  that  character  is 
homozygous  and  breeds  true;  but  when  the  plant  receives 
the  character  from  only  one  parent,  the  character  is  hetero- 
zygous and  shows  segregation  in  the  next  generation.  This 
heterozygous  condition,  though  not  fixable  itself,  since  it 
always  breaks  up  in  the  succeeding  generation,  is  a  valuable 
asset  to  the  plant  breeder  if  properly  utilized  and  a  distinct 
disadvantage  if  unrecognized. 

The  fusion  of  two  gametes  into  a  zygote  which  is  known 
as  fertilization  effects  two  very  different  results:  first,  a 
union  of  the  hereditary  factors  possessed  by  these  gametes; 
second,  a  stimulation  to  the  cell  division  necessary  for 
normal  development.  Probably  in  every  case  where  fer- 
tilization can  take  place  at  all  there  is  a  certain  amount  of 
this  stimulus  to  development,  but  the  fact  of  especial  interest 
to  plant  breeders  is  that  this  stimulus  is  generally  far  greater 
in  a  hybrid  or  heterozygote  than  it  is  in  a  pure-bred  or 
homozygous  individual.  The  stimulus  is  simply  toward 
greater  and  quicker  cell  division  and  affects  only  size  and 
rapidity  of  maturity. 

The  tobacco  genus  (Nicotiand)  furnishes  an  admirable 
type  illustration  of  the  stimulus  due  to  heterozygosis  because 
the  species  are  generally  self-fertilized  under  natural  con- 
ditions. The  stamens  and  the  pistil  are  about  the  same 
length,  and  since  the  pollen  is  usually  shed  before  the  flower 
opens,  self-pollination  must  occur  unless  foreign  pollen  is 
carried  to  the  unopened  bud  by  insects.  When  varieties 
of  the  common  tobacco  N.  tabacum  are  crossed  together, 
the  first  hybrid  generation  is  nearly  always  from  5  to  50 


Application  of  Biological  Principles  to  Plant  Breeding     115 

per  cent  taller  than  the  average  of  the  parents.  The 
hybrids  also  have  somewhat  larger  leaves  than  the  average 
of  the  two  parents  although  the  number  is  generally  inter- 
mediate. This  statement  is  true  in  general  for  crosses 
between  the  varieties  of  most  other  species.  When  true 
species  are  crossed,  however,  the  behavior  of  the  first  hybrid 
generation  is  somewhat  different.  Sometimes  there  is  a 
great  increase  in  vigor.  N.  tabacum  X  N.  syhestris  gives 
hybrids  that  are  nearly  double  the  average  height  of  the 
parents.  N.  tabacum  X  N.  alata,  on  the  other  hand,  gives 
hybrids  that  are  less  than  one-fourth  the  size  of  the  smaller 
parent.  Both  of  these  crosses  are  sterile,  so  that  the  differ- 
ence in  behavior  cannot  be  correlated  with  sterility.  One 
can  simply  say  that  species  vary  in  their  affinity  to  cross 
with  other  species.  All  gradations  are  found,  from  those 
that  produce  full  quotas  of  viable  seed,  to  those  where  only 
an  occasional  seed  is  found  or  where  the  capsule  simply 
develops  without  the  formation  of  seed.  And  in  general 
the  additional  vigor  of  the  first  hybrid  generation  increases 
with  the  ease  of  making  the  cross.  With  perfect  ease  of 
crossing  the  stimulus  is  roughly  a  function  either  of  the 
number  or  of  the  kind  of  character  pairs  for  which  the 
individual  is  heterozygous. 

Species  naturally  self-fertilized  like  tobacco  or  wheat 
must  get  along  without  the  increased  vigor  due  to  hetero- 
zygosis.  One  notices  the  difference  only  when  artificial 
crosses  are  made.  Species  which  in  nature  are  cross- 
fertilized,  however,  are  usually  heterozygous  for  so 
many  characters  that  one  does  not  think  of  their  vigor  as 
being  largely  due  to  this  cause.  The  fact  is  only  brought 
to  notice  when  the  species  is  self-fertilized  artificially, 
for  this  tends  to  isolate  homozygous  strains  (Fig.  49). 


n6 


Heredity  and  Eugenics 


If,  for  example,  a  commercial  variety  of  maize  is  self- 

f ertilized  for  a  number  of 
generations,  the  plants 
tend  to  become  homo- 
zygous,  to  lose  the  vigor 
due  to  heterozygosity 
and  to  become  smaller 
and  less  productive. 
This  loss  of  vigor  was 
for  years  interpreted  as 
the  direct  effect  of  self- 
fertilization.  Now  we 
know  that  it  is  simply 
the  withdrawing  of  pure 
strains  from  hybrid  com- 
binations. In  a  few 
generations  the  strains 
become  practically  pure 
and  the  loss  of  vigor 
ceases.  Some  strains  of 
maize  still  yield  remark- 
ably well  after  many 
generations  of  self- 
fertilization.  Other 
strains  are  so  poor  that 
they  can  scarcely  be 
kept  alive.  In  fact  it  is 
evident  that  they  are 
kept  alive  merely  by 
the  increased  vigor  of 
growth  due  to  continual 
natural  hybridization 
with  other  strains. 


| 


o 


Application  of  Biological  Principles  to  Plant  Breeding      117 

Since  all  commercial  methods  of  selection  in  maize,  as 
well  as  other  naturally  cross-bred  species,  have  as  their 
ultimate  goal  the  isolation  of  good  homozygous  strains  (for 
this  is  what  the  words  "selection  to  type"  mean),  it  is  quite 
evident  that  the  longer  selection  has  been  carried  on  the 
more  of  this  stimulus  due  to  heterozygosity  or  hybridity 
is  lost.  No  method  of  breeding  naturally  cross-bred  species 
therefore,  where  size  and  total  yield  are  the  main  objects, 
is  proper  unless  these  facts  are  taken  into  consideration 
and  the  methods  so  modified  as  to  utilize  them.  This  is 
done  by  growing  only  the  first  hybrid  generation  of  crosses 
between  good  strains.  Nor  is  it  alone  in  wind-pollinated 
field  crops,  such  as  maize,  that  these  methods  are  useful. 
Horticultural  crops  such  as  tomatoes  and  eggplants  can  be 
grown  from  hand-hybridized  seed  with  a  profit  greatly 
exceeding  the  extra  cost  of  its  production.  It  may  be  that 
even  certain  trees  can  be  hybridized  to  advantage  for 
undoubtedly  Burbank's  quick-growing  walnuts  are  due  to 
this  phenomenon.  Furthermore,  it  accounts  for  the  fact 
that  all  asexually  propagated  crops  worthy  commercial 
supremacy,  such  as  grapes  and  potatoes  where  yield  is  the 
object  of  prime  importance,  are  always  hybrids.  Their 
mode  of  commercial  propagation  is  such  that  the  first 
hybrid  generation  can  be  indefinitely  prolonged. 

It  is  not  easy  to  leave  this  subject  without  mentioning 
the  important  role  which  this  growth  stimulus  due  to 
hybridity  may  have  played  in  the  evolution  of  the  higher 
plants.  In  self-fertilized  species,  for  example  the  violets, 
the  fact  that  the  hybrid  between  two  nearly  related  strains 
was  more  vigorous  than  either  parent  type  would  have 
given  it  such  an  advantage  in  the  ordinary  struggles  for 
existence  against  inhospitable  environment,  that  the  chances 
are  greatly  in  favor  of  its  surviving  to  produce  recombi- 


n8  Heredity  and  Eugenics 

nations  of  the  parental  characters  in  the  next  generation. 
And  there  is  always  the  chance  that  new  recombinations  of 
parental  characters  may  prove  better  fitted  to  survive  than 
the  old  combinations.  In  cross-bred  species  the  stimulus 
of  hybridity  holds  a  still  greater  advantage  since  even 
homozygous  strains  that  are  weak  and  could  never  exist 
alone,  may,  through  combination  with  other  strains,  be 
kept  in  existence  as  heterozygotes.  For  example,  one  finds 
in  maize  literally  thousands  of  genotypic  strains  in  a  single 
commercial  variety.  Many  could  not  exist  alone,  yet  they 
continue  to  exist  in  commercial  varieties  through  hybridity 
and  their  existence  may  be  proven  by  their  being  partially 
withdrawn  by  inbreeding.  Such  strains  may  have  great 
possibilities  in  certain  combinations  as  is  shown  in  Fig.  49. 
In  inbred  or  self -fertilized  species  such  as  tobacco,  however, 
strains  weak  in  themselves  perish  and  are  lost  to  sight 
because  there  is  no  probability  of  their  being  hybridized 
and  given  a  chance  of  showing  their  power  in  combination. 

This  one  phenomenon,  alone,  may  account  for  the 
commonness  of  cross-fertilized  species  and  the  rarity  of  self- 
fertilized  species,  since  it  can  be  shown  that  there  is  no  evil 
effect  due  to  inbreeding  per  se. 

Passing  now  to  the  work  more  generally  included  in  plant 
breeding,  we  find  that  commercial  methods  fall  naturally 
into  two  classes,  hybridization  and  selection.  They  are 
not  really  thus  separable  since  one  must  use  selection  after 
hybridization,  but  in  the  first  category  are  classed  all 
cases  where  man  produces  hybrids  artificially.  The  main 
object  of  hybridization  is  the  shuffling  of  unit-characters 
in  the  first  hybrid  generation  and  their  recombination  and 
fixation  in  succeeding  generations.  The  object  of  selection 
is  to  withdraw  from  mechanical  mixtures  or  from  physio- 


Application  of  Biological  Principles  to  Plant  Breeding      119 


logical  mixtures  due  to  hybridity,  strains  characterized  by 
desirable  new  variations. 

Practical  procedure  in  hybridization  naturally  varies 
somewhat  depending  upon  the  exact  object  in  view.  I  will 
endeavor  to  illustrate  the  following  phenomena  as  those  of 
most  importance:  (a)  Recombinations  of  desirable  char- 
acters and  their  fixations,  including  the  production  of 
blends;  (b)  production  of  desirable  combinations  in  the  first 


FIG.  50. — Buds  of  Nicotiana  tabacum  showing  time  and  method  of  castration 

hybrid  generation  and  their  continuation  by  asexual  propa- 
gation;  (c)  production  of  fixed  first  generation  hybrids. 

If  one  is  to  begin  at  the  real  beginning  in  this  discussion, 
he  should  spend  a  moment  in  describing  the  mechanical 
operations  of  crossing  (Fig.  50).  There  are  three  important 
steps.  First  it  must  be  determined  by  experiment  what 
environmental  conditions  are  best  suited  for  normal  seed 
production.  Second,  an  intimate  knowledge  of  the  flower- 
ing habits  and  flower  structure  should  be  gained  in  order 


i2o  Heredity  and  Eugenics 

that  the  flowers  may  be  castrated  at  the  correct  time  without 
injury  and  properly  protected  from  foreign  pollination  until 
the  time  for  hybridizing.  Third,  care  must  be  exercised  in 
applying  the  pollen  of  the  proposed  male  parent,  for  both 
premature  and  delayed  pollination  inhibits  seed  formation. 

The  precise  conditions  under  which  a  cross  should  be 
made  to  be  the  most  successful  are  not  easily  determined. 
The  proper  preparation  of  the  breeding  plot  even  before 
the  plants  are  grown  is  necessary.  One  takes  it  for  granted 
that  on  most  soils  some  fertilizer  will  be  used,  for  the  plants 
must  be  normal  to  seed  well.  The  three  essential  elements 
of  soil  fertility  are  nitrogen,  potassium,  and  phosphorus, 
and  to  get  the  best  results  compounds  of  these  elements 
must  be  present  in  proper  proportions.  First,  available 
potassium  must  be  present  in  quantities  sufficient  for  the 
normal  production  of  healthy  roots,  leaves,  and  stems,  and 
a  moderate  excess  will  not  be  harmful.  If  nitrates  are 
present  in  excess,  however,  vegetative  growth  will  be  over- 
stimulated  and  seed  production  will  be  small.  A  lack  of 
phosphorus  will  produce  the  same  effect  upon  seed  pro- 
duction, but  for  a  different  reason.  Phosphorus  is  an  essen- 
tial constituent  of  the  proteid  compounds  found  in  large 
quantities  in  the  seed.  If  the  plants  are  to  be  in  the  best 
condition  for  the  production  of  good  seed  after  crossing, 
therefore,  the  soil  should  contain  just  the  right  amount  of 
nitrates  for  a  normal  vegetative  growth,  and  a  generous 
supply  of  potash  and  phosphates.  The  exact  amounts 
must  be  determined  by  experiment  for  each  soil  and  each 
species  of  plant. 

External  conditions  that  are  also  under  partial  control 
of  the  breeder  are  available  moisture  through  irrigation  and 
sunlight  by  proper  spacing  or  artificial  shading. 


Application  of  Biological  Principles  to  Plant  Breeding      121 

Other  necessary  knowledge  that  can  be  obtained  only 
from  experience  is,  which  are  the  best  flowers  on  the  plant 
to  serve  as  parents  of  the  cross  and  what  is  the  proper  time 
for  their  pollination.  For  example,  in  the  grasses  the  first 
flowers  that  appear  usually  form  larger,  healthier  seed  than 
the  later  blossoms.  In  most  of  the  Solanaceae,  the  petunias, 
browallias,  etc.,  the  exact  opposite  is  true.  The  time  when 
the  individual  flower  is  most  receptive  to  pollen  is  even  more 
narrowly  limited.  Both  premature  and  delayed  pollina- 
tion is  the  cause  of  many  failures  and  the  optimum  time 
should  be  accurately  determined.  Having  exercised  these 
precautions,  it  remains  to  study  carefully  the  structure  of 
the  flower  in  order  that  it  may  be  emasculated,  i.e.,  the 
anthers  removed  before  the  pollen  is  shed,  with  sufficient 
adroitness  that  neither  the  anthers  shall  be  opened  nor  the 
parts  of  the  pistil  injured.  Only  a  few  buds  upon  a  single 
flower  spike  should  be  operated  upon  if  they  are  to  be  given 
the  best  chance  of  development.  If  the  buds  are  very 
small  and  some  pollen  unavoidably  reaches  them,  it  may 
be  washed  off  with  comparative  safety  with  a  dental  syringe 
if  done  immediately.  It  is  often  recommended  that  the 
calyx  and  corolla  be  cut  away  when  emasculating.  This 
should  be  avoided  if  possible  and  the  floral  envelopes  left 
as  a  protection  to  the  pistil.  After  emasculation  the  buds 
should  be  protected  from  foreign  pollen  until  time  for 
pollination,  and  again  after  pollination  at  least  until  the 
fruits  have  begun  to  form  (Fig.  51).  This  protection  may 
be  an  ordinary  paper  bag  when  the  crossing  is  done  in  the 
field.  It  may  be  used  with  a  plug  of  cotton  around  the 
mouth  if  special  precautions  are  found  necessary.  In  the 
greenhouse  a  square  of  thin  celluloid  rolled  around  the 
flower  and  caught  with  two  rubber  bands,  each  end  being 


122  Heredity  and  Eugenics 

protected  with  absorbent  cotton  plugs,  is  a  better  device. 
It  gives  excellent  protection  and  allows  transpiration. 

But  I  must  pass  from  the  technique  of  hybridizing  to 


FIG.  51. — Impatiens  sultanl  showing  protection  of  castrated  buds  in  green- 
house. 

the  results.  They  are  much  more  interesting.  As  has 
already  been  stated,  desirable  horticultural  novelties  are 
obtained  most  frequently  by  crossing  two  plants  which 


Application  of  Biological  Principles  to  Plant  Breeding      123 

differ  in  several  transmissible  characters.  The  first  hybrid 
generation  may  be  as  uniform  as  one  of  the  pure  varieties, 
but  in  the  second  hybrid  generations  all  possible  combina- 
tions of  the  characters  of  the  two  parents  are  obtained 
provided  a  sufficient  number  of  individuals  have  been 
grown.  Among  these  combinations  many  new  and  desir- 
able types  may  be  found.  Some  of  them  are  pure  types; 
some  are  heterozygous  and  will  again  segregate.  Since 
homozygous  and  heterozygous  types  are  found  which  are 
exactly  alike  in  appearance,  the  only  way  to  determine 
which  plants  are  pure  is  to  self -fertilize  desirable  individuals 
and  raise  a  third  generation.  For  example,  N.  alata, 
a  species  with  large  white  flowers,  when  crossed  with 
N.  forgetiana,  a  species  with  small  red  flowers,  gives 
hybrids  that  are  very  uniform  in  all  their  characters.  The 
flowers  are  intermediate  between  those  of  the  parents  in 
size,  and  are  red  in  color.  In  the  second  hybrid  generation, 
there  are  16  visibly  different  color  types.  Among  these 
there  are  really  81  classes,  including  those  both  pure  and 
hybrid.  It  is  therefore  necessary  to  grow  seed  from  many 
self-fertilized  plants  for  another  generation  to  be  certain 
of  getting  pure  strains  of  each  type.  But  having  done  this, 
the  pure  types  continue  to  breed  true  in  spite  of  the  mixed 
ancestry. 

This  method  is  typical  of  the  manner  in  which  floral 
novelties  are  produced.  So  many  varieties  carry  latent 
characters  that  one  is  always  likely  to  obtain  new  things 
in  crosses.  Results  of  greater  economic  worth,  however, 
are  probably  obtained  by  combinations  made  for  a  definite 
purpose.  A  beautiful  example  of  such  work  is  afforded  by 
the  experiments  of  Biff  en.  English  wheats  have  long  been 
known  as  highly  productive  varieties,  but  they  are  very 


I24 


Heredity  and  Eugenics 


susceptible  to  a  fungus  disease  called  rust,  and  do  not  make 
first-class  bread  on  account  of  the  low  percentage  of  gluten. 
After  many  importations,  wheats  resistant  to  rust  and 
high  in  gluten  content  were  obtained,  but  these  were  not 
profitable  because  of  their  low  yields.  Biffen  then  went 

to  work  to  analyze  the 
transmissible  characters 
of  the  wheats  into  Men- 
delian  factors  by  a  large 
series  of  crosses.  This  he 
was  able  to  do.  The  rest 
was  easy.  He  has  now 
produced  by  hybridiza- 
tion wheats  that  com- 
bine the  desirable 
qualities  and  which  lack 
those  disadvantageous 
to  the  grower  and  the 
baker. 

Sometimes  a  very  sim- 
ple recombination  is  of 
very  great  commercial 
value  (Fig.  52).  The  so- 
called  Havana  type  of 
wrapper  tobacco  grown 
in  the  Connecticut 
River  valley  has  large 


FIG.  52. — Nicotiana  tabacum  variety 
"Havana."  A  stocky  habit  of  growth  with 
about  20  large  leaves. 


leaves  and  a  short  stocky  habit  of  growth.  It  produces 
1 8-2 1  leaves.  There  is  another  type  from  Sumatra  which 
has  tall  habit  of  growth  with  about  26  comparatively 
small  leaves.  These  two  types  were  crossed  by  Shamel. 
From  this  cross  a  new  type  called  the  Halladay  has  been 


Application  of  Biological  Principles  to  Plant  Breeding      125 


produced  having  the  greater  number  of  leaves  of  the  Suma- 
tra parent  and  the  stocky  habit  of  growth  and  large  leaves 
of  the  Havana  parent  (Fig.  53).  The  first  interpretation 
of  this  result  was  that  an  entirely  new  variation  had  appeared 
for  the  Sumatra  does  not 
usually  have  as  many  as 
26  leaves.  The  writer  has 
been  able  to  show,  how- 
ever, that  the  actual  strain 
of  Sumatra  used  as  the 
parent  had  an  average  of 
26  leaves,  and  data  have 
now  been  collected  which 
indicate  that  the  new 
variety  is  a  simple  recom- 
bination of  the  characters 
possessed  by  the  two  par- 
ents giving  a  strain  averag- 
ing 30-50  per  cent  greater 
yield  than  the  old  Havana 
variety  (Fig.  54). 

In  a  similar  way  Orton 
has  combined  the  edible 
quality  of  the  watermelon 
with  the  resistance  to  wilt  of 
the  citron  or  stock  melon; 
Webber  has  combined  the 
fine,  long,  strong  lint  of  the  sea-island  cotton  with  the  large 
bolls  and  productiveness  of  the  upland  cotton;  Price  has 
made  many  new  combinations  in.  tomatoes;  and  von 
Riimker  has  produced  numerous  valuable  varieties  of  rye 
and  barley.  So  the  list  might  run  on  and  on.  Hundreds 


FIG.  53. — Nicotiana  tabacum  variety 
"  Sumatra."  A  tall  habit  of  growth  with 
about  26  small  leaves. 


126 


Heredity  and  Eugenics 


of  plant  breeders  are  using  these  methods  to  produce  thou- 
sands of  new  types  annually.  Most  of  them  are  worthless, 
nearly  all  of  them  are  no  better  than  what  are  already 
in  commercial  use,  but  the  comparatively  few  that  are 


FIG.  54. — Hybrid  combining  the  desirable  qualities  of  the  "Havana"  and 
'Sumatra"  varieties. 


really  superior  repay  the  time  and  money  spent  a  thousand 
fold.  I  might  add  that  it  is  the  community  at  large  that 
is  highly  repaid,  however,  for  the  plant  breeder,  unlike  the 
inventor,  never  gets  rich  through  his  productions. 


Application  of  Biological  Principles  to  Plant  Breeding      127 

Recently,  accurately  controlled  investigations  have 
shown  that  a  strict  Mendelian  notation  will  interpret  results 
that  hitherto  had  been  given  the  name  blended  inheritance. 
For  instance,  one  may  cross  an  eggplant,  Solanum  melon- 
gena,  bearing  large  fruits  with  one  bearing  small  fruits. 
In  the  first  hybrid  generation,  fruits  intermediate  in  size  are 
produced.  Segregation  in  the  second  hybrid  generation  is 
such  that  plants  bearing  fruit  like  either  parent  can  be 
obtained  if-  a  large  number  of  individuals  (several  thousand) 
are  grown.  Yet  among  the  F2  progeny,  intermediates  still 
occur  in  large  numbers,  and  from  them  pure  types  can  be 
secured. 

Most  of  the  characters  hitherto  described  are  qualitative 
in  nature.  They  are  either  present  or  absent  in  the  differ- 
ent varieties.  Such  characters  are  generally  dominant, 
in  which  case  the  heterozygotes  are  like  the  homozygotes 
in  appearance.  Other  characters  give  heterozygotes  inter- 
mediate in  appearance,  owing  to  incomplete  dominance, 
but  these  intermediates  can  never  be  fixed.  Owing  to  their 
heterozygous  constitution  they  always  segregate  the  paren- 
tal characters  in  the  next  generation.  Size  characters  or 
quantitative  characters,  on  the  other  hand,  are  often  yery 
complex.  They  are  due  to  the  interaction  of  many  factors. 
For  this  reason  blends  may  be  obtained  in  the  F2  genera- 
tion that  are  homozygous  for  such  a  combination  of  game- 
tic  factors  that  they  always  breed  true  to  that  condition 

(Fig.  55)- 

Fortunately  it  is  not  necessary  always  to  have  plants 
that  breed  true  to  seed.  Many  commercial  plants  are 
propagated  asexually  by  bulbs,  tubers,  cuttings,  etc. 
Here  one  has  a  method  of  growing  portions  of  a  single  plant 
for  an  indefinite  length  of  time.  Fruit  trees,  bush  fruits, 


128 


Heredity  and  Eugenics 


strawberries,  potatoes,  pineapples,  and  many  other  kinds 
of  economic  plants  belong  to  this  category.  This  is  a  great 
advantage.  One  can  so  propagate  homozygous  strains  if  he 
wishes,  but  in  addition  he  has  a  means  of  utilizing  heterozy- 
gotes  that  would  not  breed  true  to  seed  and  also  of  keeping 

the  greater  vigor  that  ac- 
companies heterozygosis. 

No  better  example  of 
such  work  can  be  given 
than  that  of  Webber  on 
citrus  fruits.  The  great 
bugbear  of  the  Florida 
orange  grower  is  the  frost 
that  occasionally  comes, 
leaving  devastation  in  its 
wake.  Webber,  therefore, 
set  himself  the  definite 
problem  of  producing  a 
frost-resisting  orange.  He 
made  several  reciprocal 
crosses  between  the  com- 
mon orange  and  the  hardy 
but  worthless  trifoliate 
orange  (Citrus  trifoliate?). 
Among  the  seedlings  ob- 


FIG.  55. — Intermediate  character  of 
an  Fi  hybrid.  At  left,  Nicotiana  panicu- 
lala;\n  center,  hybrid;  at  right,  Nicotiana 
alata. 


tained,  several  have  proven 
valuable.  They  form  a  new  class  of  citrus  fruits  and  have 
been  called  Citranges.  Three  of  these  varieties  have  been 
named  the  Rusk,  the  Willits,  and  the  Morton.  The  Rusk, 
which  is  a  hybrid  of  orange  crossed  by  trifoliata,  is  a  small 
fruit  with  a  bitter  tang  like  the  pomelo.  It  makes  excellent 
marmalade  and  preserves.  The  Willits,  coming  from  a 


Application  of  Biological  Principles  to  Plant  Breeding      129 

cross  of  orange  upon  trifoliata,  is  a  rough,  but  thin-skinned 
fruit,  resembling  an  orange  in  appearance  but  a  lemon  in 
flavor.  It  is  used  as  a  condiment  or  for  citrangeade.  The 
Morton,  coming  from  the  same  kind  of  cross  as  the  Willits, 
is  a  large,  juicy,  almost  seedless  fruit,  only  slightly  more 
bitter  than  the  sweet  orange. 

Young  trees  of  these  three  varieties  have  endured  a 
temperature  of  eight  degrees  above  zero,  and  it  is  thought 
that  by  the  use  of  them  and  of  similarly  obtained  varieties, 
citrus  fruit  culture  can  be  extended  fully  400  miles  north 
of  the  present  region. 

In  connection  with  this  description  of  the  production  of 
new  citrus  fruits  it  may  be  well  to  mention  that  they  are 
sometimes  seedless.  In  fact,  seedless  fruits  are  often 
obtained  by  crossing.  In  true  annuals  reproducing  by  seed 
only,  such  productions  would  be  of  no  value,  for  they  would 
perish  at  the  end  of  the  first  season.  Seedless  perennials, 
however,  are  among  the  most  valuable  horticultural  varie- 
ties simply  because  they  can  be  propagated  asexually. 
In  floral  novelties,  moreover,  not  only  seedlessness  but 
entire  sterility  is  not  a  drawback  to  commercial  worth, 
because  sterile  plants  are  often  famous  for  their  profuse 
flower  clusters. 

It  was  stated  earlier  that  one  phenomenon  of  hybridi- 
zation was  the  production  of  fixed  or  constant  first  genera- 
tion hybrids.  This  statement  was  made  from  hearsay 
evidence.  There  are  several  cases  in  which  either  new 
characters  or  blended  characters  that  breed  true  appear 
to  have  been  formed,  but  they  have  not  been  studied  with 
sufficient  care  for  their  mode  of  inheritance  to  have  been 
accurately  and  finally  decided.  In  crosses  between  cer- 
tain true  species,  hybrids  have  been  produced  that  are 


130  Heredity  and  Eugenics 

seemingly  very  constant  and  uniform.  Perhaps  the  most 
famous  of  these  are  the  blackberry-raspberry  hybrids  first 
produced  by  the  late  E.  S.  Carman  and  later  by  Luther 
Burbank  and  others.  Several  hybrids  having  a  commer- 
cial value  have  been  made  in  this  genus  (Rubus},  and  the 
small  number  of  second  generation  progeny  that  have  been 
grown  are  said  to  have  bred  approximately  true.  Prac- 
tically, it  makes  little  difference  about  the  exactness  of  this 
statement.  One  can  simply  say  that  for  all  ordinary  intents 
and  purposes,  such  hybrids  breed  true.  To  the  scientist 
it  makes  a  great  deal  of  difference  whether  these  hybrids 
are  definite  exceptions  to  the  law  of  Mendel  or  not.  The 
few  data  that  we  have  are  not  sufficient  to  clear  up  this 
point,  but  several  hypothetical  explanations  of  the  phe- 
nomena can  be  given  that  are  in  harmony  with  a  belief  in 
the  universality  of  Mendelianism. 

Nothing  is  really  known  about  segregation  in  these 
hybrids  because  the  variations  that  occur  are  difficult  to 
describe  and  because  the  plants  have  never  been  grown  in 
large  quantities.  It  is  likely  that  numerous  separately 
heritable  characters  are  concerned  in  such  crosses  between 
true  species,  and  when  n  pairs  of  character  are  concerned 
it  takes  four  to  the  nth  power  seedlings  to  run  an  even 
chance  that  there  will  be  one  plant  like  each  of  the  parents. 
When  one  considers  that  with  ten  pairs  of  characters,  this 
means  over  1,000,000  individuals,  he  can  see  what  enormous 
numbers  are  needed  to  give  valid  conclusions.  Moreover, 
these  hybrids  are  only  partially  fertile  and  some  considera- 
tion must  be  given  the  possibility  that  selective  fertilization 
among  the  gametes  of  the  hybrid  may  occur.  To  take  a 
hypothetical  case,  suppose  two  plants  are  crossed  in  which 
the  flowers  of  one  are  twice  the  length  of  the  flowers  of  the 


Application  of  Biological  Principles  to  Plant  Breeding      131 

other  and  that  the  extra  length  of  the  longer  flower  is  con- 
trolled by  three  or  four  separately  heritable  factors.  If 
only  a  few  of  the  egg  cells  and  pollen  cells  can  fuse  on 
account  of  the  dissimilarity  of  their  gametic  constitution, 
one  would  expect  only  those  seeds  to  be  formed  that  would 
result  from  the  fusion  of  the  germ  cells  nearest  alike. 
Intermediates  would  therefore  be  more  likely  to  occur  than 
extremes. 

There  is  one  other  possible  way  of  accounting  for  con- 
stant intermediate  races.  In  crossing  species  of  the  genus 
Nicotiana,  I  have  had  plants  develop  from  carefully 
guarded  and  supposedly  hybrid  seed  that  were  exactly  like 
the  maternal  plant.  These  seeds  must  have  resulted  from 
apogamy  or  polyembryony,  that  is,  from  the  development 
of  an  immature  egg  cell  without  fertilization.  The  phe- 
nomenon was  evidently  induced  by  the  extraordinary 
irritation  of  the  foreign  pollen.  The  question  then  arises: 
May  not  the  difficulty  of  maturing  sex  cells  in  the  Ft  genera- 
tion of  a  wide  cross  sometimes  cause  apogamous  seed 
development  and  therefore  a  continued  propagation  of  a 
constant  and  uniform  race? 

These  pieces  of  work  illustrate  the  various  distinct  types 
in  the  improvement  of  plants  by  hybridization. 

Intentionally,  little  has  been  said  regarding  the  fixation 
of  desired  character  combinations  when  the  new  varieties 
obtained  are  to  be  reproduced  by  seed.  The  reason  for  this 
omission  is  that  the  selective  method  used  after  hybridiza- 
tion is  the  same  as  that  used  upon  crops  whose  small  seeds 
and  tendency  to  vary  makes  it  difficult  or  unnecessary  to 
produce  artificial  hybrids.  The  method  is  Vilmorin's  and  is 
based  upon  the  fact  that  one  cannot  tell  the  most  productive 
or  otherwise  desirable  plant  by  inspection.  The  true  basis 


i32  Heredity  and  Eugenics 

of  selection  must  be  the  average  condition  of  the  progeny 
of  a  plant  determined  by  actual  field  tests.  The  entire 
object  of  selection  is  accomplished  when  a  homozygous 
strain  or  strain  genotypical  for  the  desired  qualities  is 
isolated.  The  idea  is  simple;  to  put  the  idea  into  practice 
successfully  is  often  a  tedious  and  difficult  task. 

As  in  hybridization,  the  ease  with  which  results  can  be 
obtained  by  selection  depends  largely  upon  flower  structure. 
In  selection,  however,  the  relative  facility  with  which 
artificial  cross-pollination  can  be  accomplished  is  of  small 
importance.  _What  one  wishes  to  know  is  whether  cross- 
pollination  or  self-pollination  takes  place  naturally. 

Practically  all  plants  are  occasionally  cross-fertilized 
naturally,  and  many  of  them  have  devices  whereby  they 
are  nearly  always  crossed;  but,  as  we  have  already  seen, 
though  cross-fertilization  is  an  advantage  to  a  plant,  it  is 
not  at  all  essential.  Wheat,  for  example,  is  almost  always 
self -fertilized;  yet  it  has  kept  its  vigor  for  thousands  of 
years.  The  importance  of  this  fact  to  the  selectionist  is 
readily  seen.  If  seed  from  several  varieties  of  wheat  is 
mixed  and  planted,  each  variety  remains  true  to  its  type 
because  of  self-pollination,  and  each  strain  can  be  recovered 
in  one  generation.  In  like  manner,  if  desirable  variations 
occur  in  a  wheat  variety,  it  is  a  simple  process  to  sepa- 
rate them  from  the  parent  strain,  for  the  two  are  mixed 
mechanically.  It  is  only  necessary  to  save  seed  from 
individual  plants  and  grow  them  in  separate  rows  or  plots. 
One  can  see  immediately  whether  the  desirable  variation 
is  inherited  or  not,  and  if  so  the  thing  is  done. 

In  a  cross-pollinated  plant  the  method  is  the  same,  but 
the  work  is  not  so  easy.  The  pollen  is  carried  through  long 
distances  by  the  wind  or  by  insects,  and  even  with  carefully 


Application  of  Biological  Principles  to  Plant  Breeding      133 

isolated  plots  the  plants  are  often  intercrossed.  Each  prize 
plant  selected  for  future  breeding  will  have  had  a  few  and 
possibly  many  of  its  ovules  fertilized  by  pollen  from  less 
desirable  strains.  When  these  seeds  are  grown  they  of 
course  again  fertilize  the  ovules  of  the  desirable  plants  with 
a  frequency  proportionate  to  their  number.  In  certain 
plants  the  process  may  be  shortened  by  having  recourse 
to  artificial  self-pollination.  But  unfortunately  this  cannot 
always  be  done.  Suppose  one  were  dealing  with  red  clover 
where  the  flowers  are  small,  almost  sterile  with  their  own 
pollen  and  produce  only  one  seed.  In  such  a  crop  a  long 
and  tedious  method  of  continuous  selection  must  be  used 
for  there  is  no  other  way.  One  must  simply  keep  hi  mind 
the  supporting  principle  of  all  selection  work,  that  the 
seeds  of  single  plants  are  grown  in  isolated  plots  and  the 
character  of  the  mother  plant  is  judged  by  the  characters 
of  the  progeny. 

We  have  already  seen  from  Mendelianism  and  the  geno- 
type conception  of  heredity  why  this  method  is  the  only 
proper  one,  but  perhaps  an  illustration  will  show  the 
matter  more  clearly.  The  older  method  of  selection,  called 
variously  the  German  or  "mass  selection"  method  by  plant 
breeders  and  the  "performance  record"  method  by  stock- 
breeders, is  based  entirely  upon  the  appearance  or  general 
character  of  the  mother.  For  example,  the  German  sugar 
beet  raisers  have  for  years  analyzed  large  numbers  of 
sugar  beets  and  have  grown  their  seed  from  the  mother 
beets  showing  the  highest  percentage  of  sugar.  No  par- 
ticular attention  was  paid  to  planting  from  "blood  lines" 
of  high  sugar  content;  those  beets  were  bred  from  which 
appeared  to  be  the  best  by  their  performance  record  in  the 
polariscope  test.  A  great  many  of  these  selected  mothers 


134  Heredity  and  Eugenics 

were  simply  high  extremes  belonging  to  "blood  lines"  that 
were  low  in  their  average  sugar  content.  These  individuals 
crossed  with  those  from  better  "blood  lines"  and  progress 
was  made  very  slow  indeed. 

In  this  short  discussion  on  selection  the  writer  has 
endeavored  to  make  clear  two  points  that  may  be  sum- 
marized as  follows.  Plants  are  exceedingly  variable  but 
the  majority  of  these  variations  are  simply  accelerations 
or  retardations  of  the  development  of  the  whole  or  of  cer- 
tain parts  of  the  plant  due  to  good  or  bad  environment  at 
critical  stages  of  the  plant's  growth.  These  variations  are 
not  inherited  because  the  reproductive  or  germ  cells  are  not 
affected.  Other  variations,  however,  are  being  constantly 
produced  by  nature — though  much  more  rarely — which 
do  effect  the  reproductive  cells  and  are  transmitted  to  the 
plant's  progeny.  These  variations  are  the  basis  of  selec- 
tion. They  are  constant  from  the  beginning — although 
their  possible  presence  in  a  heterozygous  condition  may 
make  it  seem  otherwise — and  remain  so  unless  changed  by 
a  second  variation  affecting  the  same  constituent  in  the 
reproductive  cells  that  is  due  to  develop  the  character  in 
question.  The  second  point  to  be  emphasized  is  that  the 
whole  aim  and  action  of  selection  is  to  detect  the  desired 
heritable  variants  among  the  useful  commercial  plants 
and  through  them  to  isolate  a  race  with  the  desired  char- 
acters. When  such  a  homozygous  race  is  produced,  selec- 
tion can  then  do  nothing  until  nature  steps  in  and  produces 
another  desirable  variation.  The  progeny  test  is  the  way 
to  accomplish  this  end.  It  does  this  by  showing  us  to  which 
strains  each  mother  plant  belongs.  It  is  a  sure  test  whether 
the  heterozygous  condition  is  simple  or  complex.  If  it  is  a 
question  of  which  seeds  of  a  maize  ear  are  homozygous  and 


Application  of  Biological  Principles  to  Plant  Breeding      13,5 

which  are  heterozygous  for  starchiness  the  matter  is  cleared 
up  at  once.  If  it  is  a  question  of  which  of  a  lot  of  beans  is 
homozygous  for  the  gene-complex  of  large  size,  the  com- 
plexity of  factors  concerned  may  require  a  greater  number 
of  progeny,  but  the  test  is  valid  in  the  end. 

There  remains  for  mention  a  phenomenon  of  some  inter- 
est even  though  it  has  produced  few  varieties  of  plants  of 
commercial  importance.  This  is  the  sudden  appearance 
of  a  branch  with  characteristics  different  from  the  mother 
plant  upon  which  it  is  borne  that  may  be  cut  off  and  propa- 
gated asexually.  It  is  the  so-called  bud  sport.  It  is  of 
practically  no  importance  outside  of  the  production  of  floral 
novelties.  Perhaps  this  is  accounted  for  by  the  fact  that 
bud  variations  nearly  always  affect  the  same  characters 
that  have  previously  been  changed  in  the  same  way  through 
seed  variations.  Furthermore,  the  change  is  practically 
always  the  loss  of  a  character  which  leaves  little  oppor- 
tunity for  the  production  of  the  real  novelties  through 
progressive  variations  (Fig.  56). 

The  production  of  the  smooth-skinned  peach,  the  nec- 
tarine, as  a  sport,  from  the  ordinary  peach  tree,  is  the  classi- 
cal example  of  this  type  of  variation.  This  is  undoubtedly 
simply  the  loss  of  the  Mendelian  factor  for  presence  of  the 
down  upon  the  fruit,  and  might  be  expected  to  come  about 
through  some  abnormal  cell  division  in  much  the  same  man- 
ner that  variations  occur  in  the  reproductive  cells.  They 
are  usually  not  inherited  through  the  seeds.  This  is  what 
would  be  expected.  It  is  said,  however,  that  sometimes 
such  variations  come  perfectly  true  to  seed.  If  this  is  so, 
one  must  suppose  that  the  varying  plant  cell  was  one  which 
could  give  rise  to  the  reproductive  cells.  Since  nothing 
definite  is  known  of  this  matter,  however,  speculation  does 


136 


Heredity  and  Eugenics 


not  seem  wise.    It  is  simply  mentioned  as  one  other  way  in 
which  new  plant  varieties  originate. 

In  conclusion  I  wish  to  anticipate  a  possible  question. 


FIG.  56. — Frond  of  Boston  fern  and    types   that  have  arisen  through  bud 
variation. 

What  help  have  the  new  biological  principles  been  to  the 
commercial  plant  breeder?  A  prominent  horticulturist 
has  said  that  the  new  discoveries  have  made  necessary  no 
changes  in  method.  With  the  exception  that  they  have 


Application  of  Biological  Principles  to  Plant  Breeding     137 

shown  the  scientific  basis  for  Vilmorin's  method  of  selection, 
which  before  was  not  in  general  use,  the  statement  is  largely 
true.  Yet  they  have  been  of  inestimable  practical  value. 
They  are  time  savers.  In  hybridization,  one  no  longer 
grows  large  quantities  of  first  generation  hybrids  and  small 
quantities  of  second  generation  hybrids,  for  he  knows  that 
it  is  in  the  second  generation  that  the  desirable  recom- 
binations of  characters  will  occur.  In  many  cases  he  can 
even  predict  with  some  accuracy  the  exact  number  of  second 
generation  individuals  which  it  will  be  necessary  for  him 
to  grow  to  obtain  the  desired  result.  And  even  when  this 
cannot  be  done  he  knows  that  the  blended  characters  of 
the  first  hybrid  generation  do  not  mean  that  he  has  failed 
to  attain  his  object.  It  is  simply  a  matter  of  growing  large 
numbers  in  the  second  hybrid  generation  that  insures 
success.  Furthermore,  the  plant  breeder  has  a  means  at 
hand  to  show  what  characters  are  heterozygous  and  there- 
fore unfixable.  He  therefore  no  longer  wastes  time  hi 
striving  for  a  pure  strain  of  a  heterozygous  type  such  as  the 
Blue  Andalusian  fowl.  Nor  does  he  still  regard  the  appear- 
ance of  "rogue"  plants  in  his  nursery  beds  as  a  necessary 
affliction  of  Providence.  He  has  learned  that  they  are 
simply  recessive  segregates  and  can  be  prevented  by  prop- 
erly protected  hand-pollinations. 

In  the  field  of  selection  the  new  ideas  are  still  more 
economical  of  time.  To  the  belief  that  faith  and  continu- 
ous selection  toward  an  ideal  would  produce  any  desired 
result  has  succeeded  the  idea  that  nature  alone  produces 
variations  and  that  man's  duty  is  to  be  alert  to  grasp  their 
possibilities  and  to  make  the  most  of  them.  No  longer  is 
it  believed  that  many  generations  of  work  are  necessary 
to  purify  a  commercial  variety  of  plants  from  undesirable 


138  Heredity  and  Eugenics 

characters.  No  longer  is  there  belief  that  the  results  of 
selection  are  continuous,  that  it  gradually  perfects  a  char- 
acter. We  work  for  strains  homozygous  for  characters 
that  we  know  are  there,  and,  by  our  direct  methods  we  get 
them  without  loss  of  time. 


WILLIAM  LAWRENCE  TOWER 

Associate  Professor  of  Zoology,  the  University  of  Chicago 


CHAPTER  VII 

RECENT  ADVANCES  AND  THE  PRESENT  STATE  OF 
KNOWLEDGE  CONCERNING  THE  MODIFICATION  OF 
THE  GERMINAL  CONSTITUTION  OF  ORGANISMS  BY 
EXPERIMENTAL  PROCESSES 

INTRODUCTION 

Through  inheritance  there  comes  the  rhythmic  repeti- 
tion in  each  specific  organic  form  of  a  precise  and  definitely 
repeated  series  of  events  ending  in  the  production  of  an 
individual  which  in  time  sets  free  from  itself  a  highly  organ- 
ized and  specific  mass — a  gamete,  which,  when  properly 
combined  with  some  other  gamete  and  nurtured,  repeats 
again  the  series  of  events  which  took  place  in  the  parent 
bodies  which  preceded  them.  Throughout  all  of  this  com- 
plex, rhythmic  process  a  material  basis,  the  germ  plasm, 
keeps  intact  from  parent  to  progeny  genetic  lines  of  descent. 
This  continuity  of  material  basis — first  clearly  recognized 
by  Gustav  Jaeger,  and  later  woven  by  Weismann  into  his 
germ-plasm  theories — while  known  in  its  gross  appear- 
ance and  many  of  its  behaviors,  is  nevertheless  quite 
unknown  as  regards  its  real  constitution  and  the  means 
through  which  it  does  reproduce  so  accurately  in  each 
generation  the  sequence  of  events  characteristic  of  its 
specific  organic  form. 

The  purely  a-priori  hypotheses  of  the  "constitution" 
of  this  substance  in  reality  help  us  little  or  not  at  all  as  a 
basis  for  experimental  investigation.  The  id-determinant- 
biophore  fabric  of  Weismann,  Naegeli's  micellae  chains, 

141 


142  Heredity  and  Eugenics 

DeVries'  pangene  complex  are  no  better  and  perhaps  no 
worse  than  the  hypothesis  that  racial  memory  is  the  basis 
of  inheritance,  or  that  the  complex  or  harmonious  equi- 
potential  systems  of  Driesch  "explain"  the  phenomena. 

As  far  as  the  facts  of  development  and  heredity  are 
concerned,  they  might  go  on  indefinitely  repeating  any 
given  series  of  events,  but  there  would  be  only  one  type  of 
organism,  alike  at  any  and  all  points  in  the  genetic  chain. 
Adequate  evidence  that  there  have  been  changes  in  this 
series  of  events  in  the  past  and  that  changes  are  now  going 
on  is  found  in  the  array  of  specific  organic  forms  that  exist 
and  have  existed  through  geological  history.  How  have 
these  changes  been  produced  ? 

The  nineteenth-century  biology  formulated  its  hypothe- 
ses around  two  widely  different  concepts;  an  extreme 
transmission  hypothesis  in  which  modifications  arising  in 
peripheral  parts — soma,  i.e.,  personal  peculiarities  developed 
in  life — are  transmitted  to  the  progeny,  through  being  in 
some  manner  incorporated  into  the  germinal  constitution  of 
the  race ;  and  the  hypothesis  that  changes  in  the  race  arise 
primarily  in  the  germinal  substance  itself  and  appear  later 
in  the  soma. 

The  idea  of  the  peripheral  origin  of  variations  through 
the  stress  of  the  conditions  of  life  dates  back  to  Buff  on, 
Erasmus  Darwin,  and  Lamarck,  whose  ignorance  of  things 
now  common  knowledge  had  led  them  to  express  the  opinion, 
backed  by  much  circumstantial  evidence,  that  the  condi- 
tions of  life,  especially  when  changed,  produced  variations 
which  were  heritable  in  the  race.  Darwin  advanced  the 
hypothesis  of  an  atomistic  mechanism  whereby  this  trans- 
mission could  conceivably  be  produced  and  upon  this  pro- 
visional hypothesis  of  Pangenesis  have  been  based  all 


Modification  of  Germinal  Constitution  of  Organisms      143 

subsequent  hypotheses  of  the  peripheral  origin  of  modifi- 
cations and  of  their  inheritance. 

The  hypothesis  of  the  peripheral  origin  and  transmission 
of  variations  is  shown  in  diagram  in  Fig.  57-4,  where  the 
cause  of  variation  (x)  impinges  upon  the  organism  and 


External  cause  of  somatic 
modification 


PARENTS 


PROGENY 


FIG.  57. — (A),  Diagram  to  represent  Darwin's  Provisional  Hypothesis  of 
Pangenesis  and  current  neo-Lamarckian  conceptions  and  (B),  the  continuity  of 
the  Germ  Plasm  Hypothesis  of  Weismann. 

induces  a  change,  variation  (y),  and  from  the  cells  composing 
this  modified  part,  as  from  all  other  cells  of  the  body, 
gemmules,  minute  masses  of  matter,  electrolites,  or  some- 
thing, are  thrown  off  and  these  units  conserve  the  power  of 
reproducing  the  replica  of  the  part  from  which  they  come, 
either  normal  or  modified.  These  gemmules  are  supposed  to 
be  gathered  in  the  gametes,  and  in  reproduction  are  supposed 


144  Heredity  and  Eugenics 

to  be  redistributed  peripherally  and  to  reproduce  the  dupli- 
cate of  the  particular  character  from  which  they  arose. 
If  now  (x)  impinging  upon  the  organism,  gives  (y)  a  new 
variation,  then  new  sorts  of  gemmules  are  supposed  to  be 
formed,  and  these  on  being  gathered  up  and  carried  along  in 
reproduction  by  the  gametes  will  cause  to  reappear  in  the 
progeny  the  modified  character.  Repeated  impact  of  (x) 
may,  in  the  opinion  of  the  adherents  of  the  view,  succes- 
sively increase  (y).  All  theories  of  the  peripheral  origin 
and  inheritance  of  variations  are  patterned  after  Darwin's 
hypothesis,  and  although  they  have  different  expressions  or 
terms  for  the  carriers  of  the  variation:  nerve  force,  force, 
ions,  electrolites,  energy,  etc.,  they  are  in  essence  the  same 
conception  and  are  all  operated  by  the  same  mechanism. 

Radically  opposed  to  this  theory  of  the  peripheral  origin 
of  variation  is  that  of  the  central  or  germinal  origin  of  varia- 
tion, in  which  the  cause  (x)  acts  upon  the  germ  and  pro- 
duces the  change  in  the  germinal  constitution  which,  when 
the  germ  undergoes  development,  produces  the  divergent 
character  (y),  the  variation  (Fig.  57$). 

Much  logic  has  been  expended  upon  this  problem  of 
transmission.  Weismann  has  made  a  masterly  analysis 
of  the  situation  and  can  discover  no  reason  for  any  con- 
clusion other  than  in  favor  of  the  germinal  or  central  origin 
of  all  variations  that  are  efficient  hi  evolution.  Spencer, 
Cope,  Eimer,  Semon,  Rignano,  and  others  have  tried  to 
equal  Weismann's  logical  analysis  of  the  problem,  but 
without  any  conspicuous  success.  The  problem  is  one  for 
experiment  and  not  for  solution  by  logic. 

Very  tiresome  are  the  multitude  of  arguments,  and  the 
arrays  of  "plausible  instances,"  and  of  the  "facts"  which 
"can  only  be  explained"  thus  and  so.  Many  times  has  the 


Modification  of  Germinal  Constitution  of  Organisms      145 

whole  field  been  gone  over  and  summarized,  and  yet  one  sees 
no  progress,  nor  can  progress  be  expected  from  this  method 
of  attack.  Only  precise  experimental  procedure  can  in  any 
way  aid  in  the  solution  of  the  problem,  and  all  too  often  the 
experiments  to  test  these  theories,  especially  the  earlier  ones, 
admit  of  diverse  interpretations,  so  that  they  are  in  the  main 
inconclusive. 

In  this  chapter  are  presented  some  of  the  data  accumu- 
lated in  recent  efforts  to  gain  precise  experimental  knowl- 
edge of  how  germinal  changes  are  brought  about.  I  shall, 
therefore,  present  in  two  divisions  the  data  and  conclusions 
bearing  upon  the  two  supposed  methods  of  change,  with 
such  brief  discussion  and  correlation  of  the  already  over- 
discussed  and  over-correlated  literature  as  may  be  necessary. 

THE  TRANSMISSION  OF  SOMATIC  VARIATIONS 

It  has  been  proved  that  variations  do  arise  primarily  in 
the  germinal  substance,  and  appear  secondarily  in  the  soma; 
but  can  it  be  proved  that  modifications  arising  in  the 
soma  are  transmitted  to  and  incorporated  into  the  germinal 
constitution  and  appear  in  subsequent  generations?  It  is 
apparent  that  properly  planned  and  conducted  experiments 
are  alone  of  service  in  the  attempt  to  solve  this  question. 

It  in  no  wise  strengthens  the  position  of  the  supporters 
of  the  theory  of  the  peripheral  origin  of  variations  to  present 
an  extensive  array  of  examples  not  explicable  excepting 
through  the  use  of  this  idea,  and  even  though  it  "does 
explain"  and  "may  explain"  a  huge  array,  or  even  all  of  the 
problems  of  evolution,  it  does  not  thereby  become  a  proven 
truth.  Special  creation  equally  well  explains  all  the 
phenomena,  if  certain  assumptions  be  accepted  as  true. 
However,  not  until  this  or  any  other  form  of  transmis- 


146  Heredity  and  Eugenics 

sion  can  be  obtained  in  properly  guarded  experiments  and 
reproduced  at  will,  can  the  process  be  admitted  as  a  true 
evolutionary  process. 

The  problem,  therefore,  is  to  produce  "somatic  variations" 
in  a  soma  at  such  a  time,  or  in  such  a  fashion,  that  the  germ 
cells  will  not  be  affected  by  the  action  of  the  incident  forces 
used,  and  then  by  breeding  discover  if  the  change  appears  in 
the  progeny  arising  from  the  unstimulated  germs.  Evi- 
dence of  somatic  influence  upon  germinal  material  may  also 
be  obtained  by  transplanting  germ  glands,  especially  ovaries, 
into  different  somas,  as  has  been  done  by  several  experi- 
menters.1 

The  recent  experiments  of  Guthrie,2  Castle,3  and  Daven- 
port4 are  well  adapted  to  showing  any  possible  action  of  the 
soma  upon  the  germ.  In  Guthrie's  experiments  proper 
care  was  apparently  not  taken  to  determine  the  character 
of  the  stocks  used  and  to  preclude  the  possibility  of  regener- 
ated ovaries.  Therefore  his  results  are  not  conclusive. 
Guthrie  describes  his  experiments  in  the  ingrafting  of  ovaries 
between  young  females  of  single-combed  black  and  single- 
combed  white  leghorns,  as  follows: 

During  the  summer  of  1904  I  exchanged  the  ovaries  between  two 
black  and  two  white  leghorn  pullets,  weighing  about  650  gms.  each. 
One  black  and  one  white  pullet  were  saved  for  controls.  All  did  well 
for  some  time  after  the  operations,  but  during  the  winter,  before  the 
laying  season  began,  their  condition  became  extremely  poor,  owing 
largely  to  being  kept  in  inappropriate  quarters. 

1  Castle  has  recently  given  a  comprehensive  resume  of  the  ingrafting  of  germ 
glands  to  which  reference  should  be  made  for  more  detailed  consideration.  W.  E. 
Castle  and  J.  C.  Phillips,  On  Germinal  Transplantation  in  Vertebrates,  Carnegie 
Institution  of  Washington,  No.  144,  191 1. 

'  C.  G.  Guthrie,  "Further  Results  of  Transplantation  of  Ovaries  in  Chickens," 
Jour.  Exp.  Zool.,  V(  1908). 

3  Ibid.,  1911. 

4  C.  B.  Davenport,  Proc.  Soc.  Exp.  Biol.  and  Med.,  VII  (1910),  168. 


Modification  of  Germinal  Constitution  of  Organisms      147 

On  August  25,  1906,  another  series  of  pullets  of  the  same  strains 
were  similarly  operated  upon,  controls  being  saved  as  before.  They 
weighed  about  750  gms.  each,  the  white  ones  being  slightly  the  heavier. 
All  did  well  after  the  operation.  No  marked  differences  in  egg  produc- 
tion were  found  between  the  control  and  operated  hens,  nor  in  the 
fertility  of  the  eggs.  The  operated  hens  at  the  beginning  of  the  laying 
season  were  somewhat  lighter  than  the  controls.  In  other  respects 
no  differences  were  observed  in  either  the  hens,  eggs,  or  chicks. 

The  eggs  became  fertile  in  two  to  four  days  after  mating  and  on 
cessation  of  mating  the  eggs  became  infertile  in  eleven  to  nineteen 
days,  the  majority  becoming  so  on  the  fifteenth  day.  Control  hens 
BI  and  Wi)  mated  to  the  rooster  of  the  same  breed  gave  uniformly 
black  fetuses  and  chicks  in  the  case  of  the  black  hen,  and  white  fetuses 
and  chicks  in  the  case  of  the  white  hen. 

The  normal  black  chicks  had  grayish-yellow  breasts  and  throats 
and  frequently  the  under  surface  of  the  tops  of  the  wings  was  light 
colored  as  well,  but  the  plumage  of  the  entire  dorsal  surface  was  always 
solid  black.  The  light-colored  areas  on  the  ventral  surface  were 
uniformly  black  after  the  first  moult.  Occasionally  a  normal  black 
may  retain  one  or  several  white  feathers  in  the  tip  of  the  wing  per- 
manently, but  this  is  of  rare  occurrence  and  such  white  feathers  have 
not  been  observed  in  any  other  situation. 

The  normal  white  chicks -were  pure  white  to  light  buff  when  hatched, 
but  after  the  first  moult  they  were  always  pure  white.  The  black 
hen  (B2),  carrying  an  ovary  from  a  white  hen  (W2)  mated  to  the  white 
rooster,  gave  about  equal  numbers  of  white  and  spotted  fetuses  and 
chicks.  (In  all  cases  of  very  small  white  fetuses,  spots  may  have  been 
overlooked.) 

The  white  hen  (W2),  carrying  an  ovary  from  a  black  hen  (B2) 
mated  to  the  white  rooster,  gave  white,  black,  and  spotted  fetuses  and 
chicks.  The  spotted  ones  outnumbered  the  others  combined. 

The  black  hen  (B2),  carrying  an  ovary  from  a  white  hen  (W2)  mated 
to  the  black  rooster,  gave  ordinary  black,  and  black  fetuses  and  chicks 
with  white  legs,  in  about  equal  numbers.  In  regard  to  the  chicks  from 
this  hen  described  as  ordinary  black,  some  doubt  exists  as  to  whether 
the  ventral  light-colored  area  described  for  normal  black  chicks  was 
not  lighter  and  greater  in  extent  in  all  cases  than  in  the  normal  chicks, 


148  Heredity  and  Eugenics 

The  white  hen  (W2),  carrying  an  ovary  from  a  black  hen  (B2) 
mated  to  the  black  rooster,  gave  uniformly  spotted  chicks,  i.e.,  white 
chicks,  with  black  spots  on  the  dorsal  surface  of  the  head,  neck,  wings, 
back,  or  on  the  tail. 

Owing  to  the  uniform  results  from  the  controls,  it  may  be  assumed 
that  the  strains  of  chickens  used  breed  true  to  color.  Therefore  any 
variations  in  the  offspring  of  the  operated  hens  were  due  to  other 
influences. 

The  fact  that  in  all  cases  of  the  operated  hens,  white  or  black  or 
spotted  fetuses  or  chicks  were  produced  (i.e.,  the  offspring  showed 
variations  from  the  normal  in  color  markings)  shows: 

1.  That  the  eggs  from  each  of  the  operated  hens  were  from  the 
transplanted  ovary.    Take  hens  B2  and  W2.    These  hens  were  bred  to 
the  roosters  of  their  color.    Had  some  portion  of  their  own  ovary  not 
been  removed  at  the  time  of  the  operation  (a  remote  possibility)  and 
was  functioning,  then  we  would  have  expected  solid  offspring  Like  the 
controls.    But  such  was  not  the  case.    In  the  offspring  from  B3,  in 
which  the  male  and  foster  mother  were  black,  black  predominated  but 
white  occurred.    This  must  have  come  through  the  white  ovary.    In 
the  offspring  of  W2,  in  which  the  male  and  foster  mother  were  white, 
white  was  the  predominating  color  but  black  occurred.    The  black 
therefore  must  have  come  from  the  black  ovary. 

If  we  accept  the  statement  that  in  ordinary  crossing  of  black  and 
white  breeds  the  white  is  dominant,  then  we  assume  that  the  same  is 
not  true  for  this  kind  of  (female)  crossing,  or  that  the  original  color 
influence  was  more  strongly  preserved  in  the  black  than  in  the  white 
ovary.  From  the  constancy  in  the  results  in  the  above  two  hens,  we 
may  conclude  that  the  ovaries  transplanted  into  the  other  two  hens, 
B2  and  W3,  were  the  ones  functioning  during  the  laying  season  also. 

2.  The  foster  mother  exerted  an  influence  on  the  color  of  the 
offspring.    Take  hens  B2  and  W3.    These  hens  were  bred  to  the  rooster 
of  the  opposite  color,  i.e.,  the  color  of  the  transplanted  ovary.    Yet  in 
the  former  the  majority,  and  in  the  latter  all  of  the  offspring  were 
spotted,  i.e.,  white  with  black  spots  on  the  dorsal  surfaces.    In  B2  the 
male  and  ovary  were  white  and  the  foster  mother  black;  in  W3 
the  male  and  ovary  were  black  and  the  foster  mother  white.    In  both 
cases  white  predominated  in  the  offspring.    It  would  seem,  therefore, 


Modification  of  Germinal  Constitution  of  Organisms       149 

if  we  leave  the  question  of  dominance  out  of  account,  that  the  foster 
influence  of  the  white  hen  was  stronger  than  that  of  the  black  hen.  If, 
on  the  other  hand,  we  consider  the  foster  influence  equal  in  both  cases, 
then  we  can  explain  the  results  as  due  to  the  dominance  of  the  white 
in  the  male  or  ovary. 

Guthrie's  contention  is  that  the  ovaries  were  wholly 
removed,  and  did  not  regenerate;  that  the  ingrafted  ovaries 
developed,  functioned,  and  were  influenced  by  the  foster 
soma  to  produce  changes  in  gametic  constitution.  The 
doubtful  points  are  concerning  the  nature  of  the  stock 
and  its  gametic  make-up,  which  was  not  tested  in  adequate 
manner,  and  the  gametic  constitution  of  all  fowls  is  known  to 
be  very  complex  (cf.  Bateson,  Saunders,  Davenport,  and 
others) ;  and  the  possibility  of  regenerated  ovaries.  Daven- 
port has  repeated  the  experiments  on  other  but  well-known 
stocks,  and  summarizes  his  findings  as  follows: 

To  test  these  experiments  [Guthrie's]  I  transplanted  ovaries  from  a 
cinnamon-colored,  heavy-boot,  pea-combed,  low-nostriled  hen  which 
breeds  true  to  a  white,  non-boot,  V-combed,  five-toed,  high-nostriled 
hen,  and  mated  her  with  a  cock  whose  characters  resembled  those  of 
the  hen  from  which  the  eggs  had  been  borrowed.  Had  the  engrafted 
ovary  been  functional,  the  chicks  must  have  all  been  like  the  cock. 
Actually,  they  were  exactly  what  expectation  calls  for  when  such  a 
cock  is  mated  to  such  a  hen  like  the  so-called  foster  mother.  The 
engrafted  eggs  are  not  functional;  the  ovary  had  degenerated. 

Six  experiments  of  this  sort  were  made  altogether  and  in  no  case 
was  there  evidence  of  a  functional  graft;  far  less  of  an  influence  on  the 
eggs  of  the  foster  mother's  soma. 

These  experiments,  made  on  better-known  stock,  with 
many  sources  of  error  constantly  in  mind,  give  exactly  con- 
tradictory results.  Equally  convincing  and  identical  in 
result  are  the  investigations  of  Castle  in  guinea-pigs,  where 
no  effect  of  the  foster  soma  upon  the  ingrafted  ovary  was 


150  Heredity  and  Eugenics 

found.  Castle  has  made  extensive  transplantations  of 
ovaries,  especially  in  guinea-pigs,  and  finds  that : 

Out  of  seventy-four  cases  six  died  as  the  immediate  result  of  the 
operation;  four  of  these  were  cases  in  which  a  ventral  incision  was  tried. 

Summarizing  the  results  of  his  operations  he  finds  that  in 

the  results  of  the  entire  series  only  one  grafted  animal  had  young 
from  her  grafted  tissue;  grafted  ovaries  functioned  in  six  other  cases, 
but  did  not  produce  young.  Ten  animals  regenerated  then-  own  ovaries, 
and  three  of  these  had  young.  Forty-two  showed  post-mortem  com- 
plete atrophy  of  the  genital  tract  and  absence  of  ovarian  tissue.  The 
remainder  comprises  fifteen  cases  in  which  results  were  not  fully  deter- 
mined. 

On  January  6,  1909,  the  left  ovary  was  removed  from  an  albino 
guinea-pig  (Fig.  58.8),  then  about  5  months  old,  and  the  ovary  of  a  pure 
black  guinea-pig  about  a  month  old  (Fig.  58^)  was  fastened  near  the 
tip  of  the  uterine  horn,  distant  a  centimeter  or  more  from  the  site  of  the 
ovary  removed.  One  week  later,  January  13,  a  second  operation  was 
performed,  in  which  the  right  ovary  of  the  albino  was  removed,  and  as 
a  graft  was  introduced  the  ovary  of  a  second  young  black  guinea-pig 
of  like  age  with  the  first  but  of  different  ancestry.  After  the  albino 
had  fully  recovered  from  the  second  operation  she  was  placed  with  an 
albino  male  (Fig.  s8C),  with  which  she  remained  until  her  death  about 
a  year  later. 

On  the  23d  of  July,  198  days  after  the  first  operation,  she  gave 
birth  to  two  female  young.  One  was  black,  but  bore  a  few  red  hairs. 
A  photograph  of  this  animal  at  the  age  of  two  or  three  months  is  shown 
in  Fig.  58.0.  The  other  young  one  was  likewise  black,  but  had  some 
red  upon  it,  and  its  right  forefoot  was  white  (Fig.  $8E). 

On  October  15  the  grafted  albino  bore  a  third  young  one,  a  male, 
which,  like  those  previously  born,  had  a  few  red  hairs  interspersed  with 
black.  A  photograph  of  this  animal  is  shown  in  Fig.  $8F. 

On  January  1 1, 1910,  the  grafted  albino  was  observed  to  be  pregnant 
for  the  third  time,  and  this  time  she  was  very  large.  Unfortunately, 
on  February  2,  she  died  of  pneumonia  with  three  full-grown  male 
young  in  utero.  The  skins  of  these  animals  were  saved  and  a  photo- 
graph of  them  is  shown  in  Fig.  586,  H,  and  K.  Like  the  other  three 


Modification  of  Germinal  Constitution  of  Organisms       151 


YOUNG  ^   PURE    BLACK   LINE   AND      SOURCE 
OF  TRANSPLANTED   OVARIES    IN   <      No  27 


O*  No.654- 

27   CROSSED  6*65A  AND 
REMAINED     TOGETHER 
UNTIL  DEATH    OF  Q 


K 


O    DIED    AND    THEIR     BLACK    COAT- 
ED FOETUSES  WERE  REMOVED 
FROM   HE:R  UTERUS 

FIG.  58. — To  show  the  lack  of  effect  of  foster  soma  upon  introduced  ova. 
(Modified  from  Castle.)     See  text  for  further  discussion  of  this  figure. 


152  Heredity  and  Eugenics 

young  they  were  black,  but  with  a  few  red  hairs  among  the  black  ones. 
They  bore  no  white  hairs. 

An  autopsy  made  an  hour  after  the  death  of  the  mother  showed  on 
the  left  side  a  distinct  ovarian  mass  about  a  centimeter  from  the  coiled 
part  of  the  oviduct;  that  is,  approximately  the  position  where  the 
graft  from  the  pure  black  guinea-pig  was  fastened  at  the  first  operation. 
On  the  right  side  the  mesentery  of  the  oviduct  was  adherent  to  the 
body  wall  where  an  incision  had  been  made  at  the  second  operation, 
and  a  small  amount  of  tissue,  regarded  as  possibly  ovarian,  was  there 
observed.  The  tissue  from  the  left  side  was  found  to  contain  numerous 
large  egg  follicles,  some  already  well  advanced,  containing  a  lymph  space; 
in  addition  a  number  of  corpora  lutea  were  observed.  On  the  right 
was  found  a  small  amount  of  undoubted  ovarian  tissue,  with  one 
well-advanced  egg  follicle,  but  the  whole  apparently  was  strongly 
encapsulated,  so  that  no  eggs  could  be  discharged  even  if  they  came  to 
maturity. 

It  is  interesting  to  note  that  both  grafts  persisted,  though  taken 
from  different  animals  and  transferred  at  different  times.  This  result 
suggests  a  possible  susceptibility  on  the  part  of  the  animal  grafted. 

Female  1,970,  a  daughter  of  the  grafted  albino,  was  mated  with 
the  albino  male,  her  father,  and  bore  three  young,  two  of  which  were 
albinos  and  one  black  with  some  red  hairs.  If  female  1,970  had  been 
the  daughter  of  a  pure  black  mother,  instead  of  a  grafted  albino,  we 
should  have  expected  her  to  produce  an  equality  of  black  and  albino 
young.  The  observed  result  was  the  nearest  possible  numerical 
agreement  with  this  expectation. 

A  control  mating  of  the  albino  male  was  made  with  a  female  of  pure 
black  stock.  As  a  result  there  were  produced  two  litters  of  young, 
including  five  individuals,  all  black,  but  with  red  hairs  interspersed. 
This  result  shows  that  the  red  hairs  found  on  the  six  young  of  the 
grafted  albino,  were  due,  not  to  foster-mother  influence  of  the  grafted 
albino,  but  to  influence  of  the  male  parent.  The  young  of  the 
grafted  mother  were  exactly  in  color  such  as  the  black  guinea-pig  which 
furnished  the  graft  herself  might  have  been  expected  to  bear  had  she 
been  mated  with  male  654  instead  of  being  sacrificed  to  furnish  the 
graft.  The  white  foot  borne  by  one  of  the  young  forms  no  exception 
to  this  statement.  Spotting  characterized  the  race  of  guinea-pigs  from 


Modification  of  Germinal  Constitution  of  Organisms       153 

which  the  father  came.  He  himself  was  born  in  a  litter  which  con- 
tained spotted  young,  whereas  neither  the  pure-bred  black  race  that 
furnished  the  graft,  nor  the  albino  race  that  received  it  was  character- 
ized by  spotting. 

Inasmuch  as  the  offspring  of  albino  parents  are  invariably  albinos, 
it  is  certain  that  the  six  pigmented  offspring  of  the  grafted  female  were 
all  derived  from  ova  furnished  by  the  introduced  ovarian  tissue  taken 
from  a  black  guinea-pig.  This  tissue  was  introduced  while  the  con- 
tained ova  were  still  immature,  and  it  persisted  in  its  new  environ- 
ment for  nearly  a  year  before  the  eggs  were  liberated  which  produced 
the  last  litter  of  three  young.  These  young,  like  the  earlier  litters, 
gave  no  indication  of  foster-mother  influence  in  their  coloration. 

The  conclusion  is  forced  upon  us  that  the  egg  cell  during  its  growth 
does  not  change  in  germinal  constitution.  Its  growth  is  like  the 
growth  of  a  parasite  or  of  a  wholly  independent  organism;  what  it 
takes  up  serves  as  food;  this  is  not  incorporated  merely  in  the  growing 
organism;  it  is  made  over  into  the  same  kind  of  living  substance  as 
composes  the  assimilating  organism. 

In  all  of  these  transplanted  germ  glands,  it  is  true,  as 
Castle  recognizes,  that  his  evidence  and  that  of  others  does 
not  disprove  the  possibility  of  foster-soma  influence,  but  it 
is  certain  that  the  evidence  is  at  present  entirely  against 
such  influence.  There  are,  however,  two  possibilities  present 
in  these  experiments  which  should  be  kept  clearly  in  view: 

1.  The  transmission  of  some  character  from  the  foster 
soma  to  the  germ  and  its  incorporation  therein. 

2.  The  power  of  the  foster  soma  to  produce  new  surround- 
ings as  a  result  of  the  transplantation,  thereby  arousing 
new  physical  or  chemical  activities  incident  upon  the  trans- 
planted germ  cells. 

If  the  first  effect  occurs  as  a  result  of  the  transplantation, 
it  is  to  be  expected  and  must  be  proven  that  some  essentially 
entire  characters  are  introduced  from  the  foster  soma  into 
the  alien  germ  cell  and  this  seems  in  all  critical  experiments 


154  Heredity  and  Eugenics 

(Castle's,  Davenport's)  not  to  have  taken  place.  As  for 
Guthrie's  experiments  with  poultry,  it  seems  as  if  Daven- 
port's adequately  controlled  and  carefully  repeated  experi- 
ments gave  results  which  show  very  clearly  that  Guthrie's 
cases  are  due  to  regenerated  germ  glands  and  impure  stocks, 
and  not  to  foster-soma  influence.  The  second  possibility, 
however,  is  a  far  different  one  and  would  show  only  varia- 
tions of  gametic  constitution  of  the  alien  germs  and  not  intro- 
duced characters.  In  other  words,  there  is  this  fundamental 
difference  between  the  two  possibilities:  the  foster  soma 
may  act  merely  as  a  new  environmental  complex  providing 
new  physical  and  chemical  states  which  may  modify  the 
physiological  activities  of  the  ingrafted  germ  cells;  and  this 
is  very  different  from  the  conception  of  the  foster  soma 
as  formulating  "a  something"  bearer  of  its  characters  or 
character,  which  "something"  it  transmits  to  the  germ, 
which  "something"  then  reproduces  in  development  the 
replica  of  the  somatic  part  or  character  from  which  it 
came. 

Neo-Lamarckians  reply  to  the  results  obtained  from 
these  grafting  experiments  by  the  statement  that  the  trans- 
planting of  ovaries  is  highly  abnormal  and  would  not  occur  in 
nature,  and  would  not  be  repeated  in  sequences  long  enough 
to  get  the  kinetic  effect  necessary  to  induce  germinal  change, 
and  therefore  the  experiments  in  no  wise  satisfy  the  require- 
ments of  their  hypothesis. 

The  idea  of  repeated  impacts  producing  an  accumulated 
kinetic  effect  only  after  long  periods  of  activity  finds  most 
complete  expression  in  the  curious  theories  of  Rignano,1 
which,  however,  are  only  another  logical  subterfuge  to 

1  E.  Rignano,  Sur  la  transmissibilite  des  caracteres  aquis.  Paris,  1906.  Also 
transl.,  Open  Court  Pub.  Co.,  191 1. 


Modification  of  Germinal  Constitution  of  Organisms       155 

maintain  the  cherished  dogma  of  the  biogenetic  repetition 
of  ontogenetic  stages  and  inheritance  through  a  transmission 
of  some  kind.  Adequate  answer  to  these  hypotheses  would 
seem  to  exist  in  the  non-inheritance  of  modifications  of  nose, 
ear,  lips,  etc.,  of  many  savage  tribes,  often  repeated  with  in- 
tense kinetic  effects  of  pain  and  stimulation,  or  of  the  feet  of 
Chinese  women,  bandaged  and  modified  through  long  series 
of  generations,  but  these  to  the  earnest  neo-Lamarckian 
are  mutilations  and  of  course  are  not  to  be  expected  to  be 
inherited.  Curiously  enough  the  "idea"  only  "works" 
in  those  instances  where  there  are  no  facts  or  evidences 
available  for  analytical  investigation. 

Distinctly  different  from  the  results  of  grafting  experi- 
ments or  the  arguments  from  plausible  interpretations  of 
past  series  of  phylogenetic  states,  are  the  interpretations 
placed  upon  many  experimental  series  not  properly  guarded. 
Thus  Semon's  interpretation  of  the  results  of  many  experi- 
mental series  is  justified  from  his  point  of  view  because  so 
many  investigations  have  not  been  sufficiently  critical  in 
orientation,  nor  in  analytical  procedure.  Thus,  for  example, 
the  experiments  of  Standfuss,  Fischer,  Pictet,  Woltereck, 
Kammerer,  Pshibram,  Zederbauer,  and  others  admit  of 
interpretations  from  either  point  of  view.  What  is  unques- 
tionably shown  is  change  in  game  tic  constitution,  permanent 
and  heritable,  but  not  capable  of  answering  the  fundamental 
questions  involved. 

That  organisms  may  be  modified  by  incident  conditions 
there  is  no  reasonable  doubt,  but  the  question  is,  how  ?  If 
the  discovery  of  the  methods  of  change  is  desired,  then 
experiments  made  upon  known  materials  under  carefully 
guarded  conditions  are  necessary,  and  are  our  only  means 
of  obtaining  real  knowledge  of  the  underlying  processes. 


156  Heredity  and  Eugenics 

It  is  obvious  that  progress  in  the  solution  of  the  problem 
can  be  made  only  through  experiments  based  upon  known 
materials  which  must  meet  certain  rigorous  requirements. 
The  experiments  of  many  observers  with  plants  and  animals 
show  clearly  that  changes  are  produced  which  are  inherit- 
able in  following  generations,  but  do  not  produce  accurate 
data  upon  critical  theoretical  points.  Thus,  for  example, 
Sumner's  recent  work  on  mice  is  entirely  of  this  order  and 
gives  only  unreliable  results.  Nor  can  experiments  give 
true  data  upon  these  points  unless  the  following  conditions 
are  complied  with: 

1.  A  stock  of  known  character,  whose  behavior,  germinal 
constitution,  variability,  etc.,  have  been  determined  for  a 
series  of  generations  and  kept  in  strictest  pedigreed  line 
cultures.     The  stock  for  experiment  must  be  clarified  and 
reduced  to  a  homogeneous  condition  as  far  as  possible, 
and  the  presence  of  minor  strains  fully  determined  and 
eliminated. 

2.  It  must  be  known  what  stages  in  the  development  of 
the  germ  cells,  if  any,  are  capable  of  being  influenced,  and 
how — by  any  force  intended  to  be  used  later  as  a  somatic 
modifier.     Further,   the  behavior  in  inheritance  of  these 
germinal  modifications,  if  any,  must  be  known  for  several 
generations. 

3.  The  somatic  change  must  be  induced  at  a  time  when 
the  germ  has  been  found  to  be  not  sensitive  to  the  stimulus 
employed,  so  that  opportunity  may  be  provided  whereby 
there  will  supposedly  be  accumulated  in  the  modified  soma 
that  something,  carrying  the  potentiality  of  reproducing 
the  modifications  which  the  soma  has  acquired  and  which  are 
believed  by  many  to  become  incorporated  into  the  growing 
germ  cells  as  part  of  their  constitution. 


Modification  of  Germinal  Constitution  of  Organisms       157 

4.  In   any   experiments   four   parallel   series   must   be 
carried :  (a)  a  parent  stock  from  which  at  the  start  is  derived 
the   experimental   stock,    (b)  the   controlled   stock  reared 
parallel  to  the  parent  stock  but  under  controlled  conditions, 
(c)  the  experimental  stock,  which  is  a  line  culture  sub- 
jected to  conditions  of  experiment  and  continued  throughout 
under  the  conditions  of  experiment,  but  from  which  is 
taken  at  intervals,  and  (d)  the  test  series,  which  are  the 
progeny  of  modified  stock  returned  to  conditions  of  the 
control  and  parent,  to  test  the  constancy  or  reappearance 
of  induced  modifications. 

5.  All  lines  must  be  group  cultures  mated  at  random  to 
obviate  in  the  fullest  possible  manner  any  traces  of  selective 
effects;    that  is,  to  breed  from  pairs  of  selected  extreme 
individuals  might  easily  lead  to  the  selective  accumulation 
of  germinal  variations  normal  to  the  race,  or  the  isolation 
of  hitherto  unrecognized  pure  lines,  and  thus  give  rise  to 
false  conclusions. 

If  these  conditions  are  complied  with  in  any  series  of 
experiments,  the  results  will  be  an  accurate  answer  to  the 
problem — no  matter  whether  brief  or  long-continued  action 
be  necessary  to  bring  about  the  inheritance — because  this 
may  also  be  tested  if  the  soma  be  modified  at  a  time  when  the 
germ  is  not  sensitive,  and  if  this  be  repeated  generation  after 
generation  the  results  obtained  become  more  and  more 
certain  in  their  value  as  evidence  for  one  or  the  other  side  of 
the  controversy. 

Furthermore,  experimental  procedure  of  this  kind  will 
at  once  give  an  answer  to  the  question  of  the  influence  of  the 
soma  as  an  environment  upon  the  germ  cell.  That  is,  by 
incident  conditions  it  is  easy  to  modify  temporarily  the 
physiological  state  of  the  soma  and  gain  further  knowledge 


158  Heredity  and  Eugenics 

concerning  the  influence  of  altered  body  states  in  producing 
germinal  variations. 

It  will  not  do  to  dodge  the  issue  as  to  experimental 
methods  by  the  citation  of  experiments  where  these  precau- 
tions have  not  been  taken  and  say,  What  matters  it,  the  end 
result  is  the  same — a  modification  ?  True,  a  modification, 
inheritable,  has  resulted  in  so  many  series  of  experiments 
that  there  no  longer  are  any  doubts  thereon.  But  that 
does  not  and  cannot  answer  the  important  theoretical 
question  because  experiments  have  all  too  often  not  been 
properly  oriented  and  guarded.  In  this  there  is  a  direct 
experimental  proof  of  the  mam  contention  of  Lamarck 
and  C.  Darwin,  that  incident  conditions  produce  permanent 
modifications.  Naturally,  in  order  to  be  permanent,  any 
departure  from  the  normal  must  become  a  part  of  the 
germinal  constitution — a  process  which  Lamarck  never 
attempted  to  explain,  and  of  which  C.  Darwin  offered 
only  a  formal  explanation  in  his  provisional  hypothesis  of 
pangenesis. 

I  have  attempted  to  obtain  what  I  considered  reliable 
data  upon  this  mooted  point  in  the  inheritance  of  somatic 
modifications,  and  one  example  of  the  results  obtained  when 
the  procedure  outlined  has  been  followed  may  be  given. 

To  determine  whether  coloration  changes  in  the  soma  produced  as  the  result 
of  changed  environmental  conditions  are  inherited,  increased,  or 
dropped  in  successive  generations. 

Conditions. — Temperature  on  the  average  6°  C.  and  relative  humid- 
ity 10  per  cent  above  that  in  nature,  with  other  conditions  natural. 
These  conditions  were  planned  to  produce  melanic  tendencies  in 
variation. 

Apparatus. — Shown  in  diagram  in  Fig.  59. 

The  experiments  in  this  series  were  conducted  in  the  years  1900  to 
1904,  and  were  carried  through  ten  lineal  generations.  The  conditions 
of  temperature  and  moisture  were  as  follows. 


Modification  of  Germinal  Constitution  of  Organisms      1 59 


i6o 


Heredity  and  Eugenics 


7  A.M. 

IO 
A.M. 

I  P.M. 

3P.M. 

8  P.M. 

Maxi- 
mum 

Mini- 
mum 

Average 

Devia- 
tion from 
Normal 

Temperature,  dry  bulb 

In  nature  

10 

22 

•21 

22 

22 

•2? 

22  .  2 

o 

In  experiment 

22 

28 

31 

31 

23 

40 

19 

28.4 

-6 

Percentage  of   relative 

humidity: 

In  nature  

*IOO 

6c 

co 

ec 

*IOO 

IOO 

4? 

74 

o 

In  experiment  

*IOO 

85 

60 

75 

*IOO 

100 

55 

84 

*Dew. 

In  this  series  of  experiments  21  per  cent  died  in  the  larval  stage 
and  9  per  cent  in  the  pupal,  while  70  per  cent  appeared  as  imagines  with 
the  proper  color  modifications.  Throughout  the  whole  series  the 
greatest  care  was  taken  to  prevent  the  conditions  of  experiment  from 
having  any  possible  influence  upon  the  germ  cells  hi  their  growth  periods 
and  during  maturation  and  fertilization.  This  was  accomplished  by 
removing  the  adults  to  normal  conditions  during  the  period  of  germ- 
cell  growth  and  fertilization,  the  fertilized  eggs  being  returned  as  soon 
as  laid  to  the  conditions  of  exDeriment. 


«.„„,„.•_         Experiment  27*,  Control 
Generations      Kept  in  Normal  Conditions 


Experiment  273,  Subjected 
to  Conditions  of  Experiment 


I  

,  .  .  .  .  276 

II  

.  .  276 

V 

Ill  

.  .  276 

'    \ 
2701 

IV.  ., 

.  .  276 

J-L 
2-jb* 

V.  ., 

.  276 

VI  

.  .  276 

2-jb1 

.L 

VII  

.  .  270 

VIII  

.  .  276 

IX  

.  .  270 

X.. 

.  .270 

270 

27d 

1 

>        4- 

270 

27a 

27<I 

270* 

27_a 

270* 

27  a* 

2-ja 

270* 

in»i 

270* 

2"ja 

^^-              ^^ 
270'" 

270* 

270 

27alft 

2-ja2 

270 

270" 

270'* 


FIG.  60. — To  show  the  different  parts  of  an  experiment,  in  which  L 
decemlineata  was  subjected  to  conditions  which  would  modify  the  soma  without 
modifying  the  germ  plasm.  The  generations  underscored  were  subjected  to  the 
conditions  of  the  experiment;  those  not  underscored  were  kept  in  natural 
surroundings. 


Modification  of  Germinal  Constitution  of  Organisms       161 

By  this  means  the  color  changes  induced  by  these  experiments  were 
known  to  be  purely  somatic  modifications.  Moreover,  a  control  series, 
derived  from  the  same  parents,  was  kept  under  normal  conditions  as  a 
check.  During  the  series  also  several  lots  were  taken  from  the  experi- 
ments and  placed  for  several  generations  in  normal  conditions,  and  were 
then  returned  to  experiment;  and  likewise  lots  were  taken  from  the 
control  and  placed  in  experiment;  and  subsequently  returned  to  con- 
trol. In  this  way  a  complete  check  was  kept  on  the  experiments.  In 
Fig.  60  are  represented  the  generations  experimented  upon  and  the 
proceedings  followed  with  each. 

The  experiment  was  divided  into  two  parts — the  experiment  proper 
(270)  and  the  control  (276).  In  270  the  beetles  were  subjected  to  the 
conditions  of  experiment  during  ten  lineal  generations,  with  results 
shown  in  Fig.  61.  A  maximum  deviation  in  coloration  was  produced 
at  once  toward  a  melanic  state  from  which  there  was  no  deviation  either 
above  or  below  in  the  succeeding  generations.  In  the  third  genera- 
tion of  270  the  progeny  were  divided  into  two  lots  of  equal  size,  one  of 
which  was  kept  in  the  conditions  of  experimentation,  and  the  other 
returned  to  natural  conditions.  This  second  lot,  known  as  27^,  after 
being  bred  during  four  generations  hi  normal  surroundings,  was  further 
separated  into  two  portions,  one  of  which  was  still  kept  in  normal  con- 
ditions as  27aia,  while  the  other  was  returned  to  the  conditions  of 
experimentation  as  27olb.  When  the  beetles  in  27^  were  returned  to 
normal  surroundings,  they  at  once  resumed  their  natural  characters 
and  did  not  deviate  therefrom  during  the  four  generations  of  270  and 
the  three  of  27aia,  or  seven  in  all.  However,  the  effect  upon  2jalb  of 
being  returned  to  the  conditions  of  experiment  was  an  immediate 
return  to  the  maximum  melanic  tendency  before  observed.  From 
the  sixth  generation  in  270  another  lot  of  beetles,  27a2,  were  taken 
and  reared  in  normal  conditions,  with  the  result  that  they  also  immedi- 
ately reverted  to  the  parental  condition,  and  the  same  was  true  of  27a3 
in  the  ninth  generation.  In  experiment  276  there  appears  a  slight 
oscillating  variability  which,  however,  is  of  no  consequence.  In  the 
second  generation  276  was  likewise  separated  into  two  lots  of  equal 
size,  one  of  which,  276,  was  retained  as  control,  while  the  other,  276', 
was  placed  in  the  conditions  of  experimentation  for  four  generations, 
and  later  in  the  seventh  generation  returned  to  control  with  276. 


1 62  Heredity  and  Eugenics 

The  effect  upon  276'  was  an  immediate  production  of  the  maximum 
melanic  condition,  which  was  retained  throughout  the  four  generations 
of  experimentation,  and  lost  only  when  2jbl  was  returned  to  control. 

In  Experiment  27  there  was  no  artificial  selection,  all  imagines  being 
allowed  freedom  to  mate  and  breed  as  in  nature;  hence  the  only 
selective  influences  present  were  those  exercised  in  the  mating  of  the 
beetles  and  by  the  conditions  of  the  experiment,  which  eliminated  a 
small  percentage. 

From  the  data  of  this  experiment  the  following  conclusions  are 
derived: 

1.  A  deviation  in  an  environmental  complex  at  once  causes  the 
polygon  of  somatic  variation  and  the  modal  class  to  shift  as  far  from 
the  normal  as  it  can  go  under  the  given  condition,  and  keeps  them  there 
until  there  is  a  return  to  the  normal  environmental  complex,  when  the 
somatic  variations  also  at  once  return  to  their  normal  state. 

2.  The  color  variations  employed  in  experiment,  which  are  purely 
somatic,  are  the  direct  result  of  a  response  to  changed  environmental 
conditions,  in  terms  of  increased  or  decreased  activity  in  pigmentation. 
They  may  change  as  rapidly,  as  frequently,  and  in  as  many  directions 
as  the  conditions  producing  them  change,  and  they  have  no  influence 
whatsoever  upon  the  coloration  of  succeeding  generations. 

This  experiment,  one  of  the  earliest  in  my  series,  illus- 
trates fairly  well  the  results  obtained  in  several  others 
carried  out  with  the  same  end  in  view.  In  all,  the  result 
has  been  a  uniform  one,  and  entirely  against  the  idea  of 
transmission  of  somatic  modifications.  I  have  had  many 
instances  when  I  thought  at  first  that  a  somatic  transmission 
had  taken  place,  but  in  all,  further  analysis  and  repetition 
clearly  showed  some  defect  in  experimentation;  and  in  no 
case  have  I  been  able  to  duplicate  one  of  these  occurrences, 
much  less  obtain  experimental  proof  of  somatic  transmission 
in  a  repetition  of  the  experiment. 

It  is  unfortunate  that  so  many  of  the  published  experi- 
mental investigations  of  this  subject  are  open  to  diverse 


Modification  of  Germinal  Constitution  of  Organisms 
Modal  class  of   parent  generations 


163 


suoi;etJEA    34;  jo 


164  Heredity  and  Eugenics 

interpretation  and  are  not  elucidations  of  the  problems. 
The  main  reason  why  this  is  so  is  that  the  materials  that 
have  been  used  and  the  methods  of  experimentation  have 
not  been  properly  guarded.  Thus,  for  example,  the  recent 
results  of  Kammerer  with  various  amphibians  and  Lacerta, 
Woltereck's  investigations  upon  Daphnia,  Zederbauer's 
experiments  with  Bursa,  Sumner's  with  mice,  as  well  as  all 
of  the  older  experiments,  admit  of  "interpretation"  from 
either  point  of  view.  Thus  Semon  "interprets"  all  of  these 
and  many  more  besides  as  showing  the  strength  of  the  neo- 
Lamarckian  position  at  the  present  time.  A  neo-Darwinian 
could  make  an  equally  good  case  of  the  same  data. 
At  present  the  conclusive  evidence  from  Castle's  trans- 
plantation of  ovaries  in  guinea-pigs,  Davenport's  negative 
results  with  poultry,  and  experiments  like  those  with  color 
in  Leptinotarsa  have  all  given  exactly  the  expected  result 
without  qualifications.  MacDougal,  in  discussing  some  of 
these  problems,  says:  "The  time  has  now  arrived  when  the 
claimants  for  neo-Lamarckianism  and  all  of  its  conclusions 
must  show  cause  for  its  further  consideration,  or  else  allow 
it  to  drop  from  the  position  of  being  seriously  taken  as  a 
method  of  evolutionary  advance." 

With  this  most  biologists  will  at  present  agree,  but 
unfortunately,  from  time  to  time,  some  careless  experi- 
menter with  more  partisan  enthusiasm  than  judgment  or 
experimental  acumen  will  come  forward  with  conclusions 
derived  from  experiments  wherein  the  most  elementary 
essentials  of  genetic  research  are  ignored  and  reassert  the 
transmission  of  somatic  changes.  Present  experimental 
evidence,  where  critical,  clearly  indicates  the  increasing 
doubtfulness  of  the  validity  of  the  hypothesis  of  somatic 
transmission. 


Modification  of  Germinal  Constitution  of  Organisms  •    165 

THE  DIRECT  MODIFICATION  OF  THE  GERM  PLASM 

Since  there  are  the  best  of  reasons  for  the  conclusion  that 
there  is  conditioned  in  the  germ  plasm  the  basis  which 
determines  the  presence  and  manifestations  of  organic 
characteristics  which  are  permanent  in  the  race  and  in  evolu- 
tion ;  and  in  that  there  are  equally  good  reasons  for  a  tena- 
cious adherence  to  the  idea  that  all  variations  which  are 
productive  of  evolutionary  changes  arise  primarily  in  the 
germ  and  appear  secondarily  in  the  soma,  it  follows  that 
any  and  all  methods  whereby  changes  are  produced  in  the 
germinal  material  are  of  paramount  interest.  Modifications 
in  this  germinal  material  are  the  basis  of  permanent  depar- 
tures from  the  racial  mean,  and  at  present  the  methods  of 
production  and  cause  of  germinal  variations  are  of  great 
practical  interest  and  value  as  well  as  of  theoretical  impor- 
tance. Germinal  variations  have  been  suggested  to  arise 
by  five  main  methods. 

The  direct  action  of  external  forces  was  the  first  to  be 
suggested  and  is  generally  admitted  to  be  an  effective  cause 
in  the  production  of  germinal  variations.  This  was  a  mode 
of  modification  suggested  by  Buffon  and  Erasmus  Darwin, 
later  elaborated  by  Lamarck,  and  made  the  basis  of  his 
theory  of  evolution  without  any  consideration  whatsoever 
as  to  whether  the  variations  were  somatic  or  germinal.  A 
half-century  later  variations  which  were  supposed  to  have 
originated  through  the  action  of  external  conditions  pro- 
vided in  the  main  the  array  of  individual  differences  upon 
which  Darwin  founded  his  theory  of  the  "origin  of  species,'' 
by  means  of  natural  selection. 

Arising  from  the  work  of  Darwin,  and  accentuated  by  the 
neo-Darwinians,  is  the  idea  of  the  production  of  variations 


1 66  Heredity  and  Eugenics 

through  selection,  but  how  selection  is  conceived  to  pro- 
duce these  results  depends  very  largely  upon  an  endless 
array  of  unproven  neo-Darwinian  assumptions. 

Hybridization  is  known  to  be  productive  of  germinal 
variations,  and  in  domesticated  organisms  a  considerable 
number  of  useful  forms  have  thus  arisen.  Frequently, 
however,  these  commercial  hybrids,  appearing  to  be  con- 
stant, are  only  first  generation  hybrids  indefinitely  per- 
petuated by  cuttings,  as  are  many  kinds  of  oranges,  apples, 
grapes,  etc.,  and  most  of  these,  if  allowed  to  reproduce 
sexually,  would  in  subsequent  generations  break  up  into 
the  component  types  out  of  which  they  were  built.  There 
is  evidence,  however,  to  warrant  the  assumption  that 
hybridization  does  result  in  the  development  of  permanent 
modifications  which  are  new  to  the  strain  in  which  they  arise, 
and  which  persist  indefinitely.  Moreover,  hybridization  is 
a  potent  means  of  creating  new  and  diverse  combinations 
of  existing  qualities  and  attributes,  which  may  account 
for  no  small  portion  of  the  "species"  in  nature,  as  well  as  in 
domestication.  To  what  extent  hybridization  is  a  source  of 
germinal  variations  in  nature  is  undetermined,  and  this 
condition  is  largely  due  to  the  persistence  of  the  dog- 
matism that  hybridization  is  of  rare  occurrence,  is  ab- 
horrent to  species  in  nature,  and  is  really  a  product  of 
domestication  and  the  supposed  loss  of  specific  integrity 
and  chastity  induced  by  man  and  cultivation.  Statements 
of  this  kind,  however,  are  entirely  a-priori  orthodox  preju- 
dices without  foundation  in  fact.  Recent  work,  especially 
by  botanists,  shows  a  considerable  and  increasing  array  of 
hybridizations  occurring  in  nature,  for  example,  in  violets, 
which  exhibit  an  abundance  of  crossings,  with  many  resulting 
hybrids.  Moreover,  this  condition  is  by  no  means  limited  to 


Modification  of  Germinal  Constitution  of  Organisms       167 

violets  or  plants,  but  is  coming  to  be  recognized  as  common 
in  nature. 

The  production  of  germinal  variations  occurs  by  combin- 
ing slightly  different  conditions  of  the  same  attribute  in  the 
zygote  (fertilized  egg) .  This  process,  amphimixis,  commonly 
advanced  by  neo-Darwinians,  has  at  present  almost  no  evi- 
dence in  support  of  the  theory  that  departures  beyond  the 
normal  range  of  variation  can  be  produced  thereby,  but  it 
is  at  least  a  conceivable  method  by  which  variations  might 
well  arise,  and  is  open  to  direct  experimental  investigation. 

The  origin  and  development  of  variations  through  the 
operation  of  orthogenesis,  a  name  descriptive  of  a  condition, 
but  personified  to  represent  the  agencies  productive  of  the 
condition  observed.  It  is  conceivable  that  changes  started 
in  one  direction  or  another  may  continue  in  that  direction 
on  the  basis  of  the  operation  of  the  law  of  inertia,  in  a 
uniform  direction  and  at  a  uniform  velocity  until  they  reach 
limits  imposed  by  the  physical  nature  of  the  part  or  of  the 
organism  in  which  they  arise,  or  until  they  reach  a  stage  of 
development  where  they  become  of  selective  value,  and  may 
be  accelerated,  retarded,  or  turned  in  other  directions. 

In  all  of  these  possible  modes  of  origin  of  germinal 
variations  two  groups  of  factors  are  always  involved:  first, 
the  physical  constitution  of  the  material,  with  its  array  of 
qualities,  attributes,  and  conditions,  which  is  always  the 
genetic  product  of  an  immense  series  of  antecedent  stages; 
second,  incident  forces  from  without  the  germinal  material. 
These  two  groups  of  factors  sustain  definite  and  fundamental 
relations  to  each  other,  and  the  effort  to  understand  the 
relations  between  these  two  fundamental  groups  has 
stimulated  much  of  the  investigation  of  the  last  decade. 
The  physical  or  gametic  constitution  is  the  constant,  and 


1 68  Heredity  and  Eugenics 

the  external  conditions  are  the  variable  in  the  complex, 
and  elimination  or  understanding  of  the  most  obvious  vari- 
able is  the  first  step  in  the  study  of  gametic  constitution 
and  modification.  Concretely,  then,  what  is  the  role  of 
external  factors  in  the  production  of  germinal  variations  ? 
Satisfactory  evidence  as  to  the  role  of  external  factors  can 
be  obtained  only  through  careful  experiments.  These  may 
be  either  experiments  under  laboratory  conditions,  or  ex- 
periments in  nature,  and,  if  possible,  both  should  be  carried 
on  at  the  same  tune  upon  the  same  materials. 

A.     The  Idea  of  Sudden  Transmutation  in  the  Germinal 
Material 

Succeeding  Darwin,  there  arose  a  group  of  followers — the 
neo-Darwinians.  Possessing  all  the  attributes  of  followers, 
unable  to  grasp  the  breadth  of  view  of  their  master,  and  see- 
ing but  a  particular  phase  of  his  general  teachings,  they 
endeavored  to  raise  that  to  undue  prominence  and  make  it 
a  universal  motive  force  in  the  evolution  of  organisms. 

The  neo-Darwinians  in  the  last  quarter  of  the  nineteenth 
century,  under  the  leadership  of  such  men  as  Weismann, 
created  what  Eimer  has  termed  the  "principle  of  omnipo- 
tent natural  selection."  It  was  attempted  to  establish  pur- 
poseful selection  as  the  sole  efficient  cause  of  variation  and 
evolution  in  organisms,  and  in  the  effort,  Weismann  went 
so  far  as  to  place  the  selective  process,  not  in  the  outside 
world,  but  in  a  microcosm  within  the  germ  plasm,  making 
it  in  every  way  incapable  of  investigation,  impossible  of 
observation,  and  all-inclusive. 

Few  today  attach  much  importance  to  Weismann 's 
"germinal  selection,"  and  the  Weismannian  theory  remains 
in  biological  history  one  of  those  curious  ideas  comparable 


Modification  of  Germinal  Constitution  of  Organisms       169 

to  the  quadrille  of  the  centrosomes.  The  last  of  the  curious 
hypotheses  developed  by  the  neo-Darwinians  is  that  weird 
phrase  of  biology  which  took  its  rise  from  the  work  of  Bates, 
Miiller,  and  Trimen,  and  which  has  been  developed  into  the 
present  theory  of  mimicry.  Its  supporters  would  have  us 
believe  that  much  transmutation  is  based  upon  a  mimetic 
principle  aided  by  the  subsidiary  principle  of  recognition 
marks.  Here  utilitarian  variation  and  purposeful  selection 
run  riot  and  produce  in  every  case  a  definite  end,  a  pro- 
tected form.  Naturally,  these  curious  and  thoroughly 
uncritical  ideas,  current  among  the  neo-Darwinians,  are 
their  own  answer. 

At  present  the  neo-Darwinian  concepts  offer  nothing 
that  is  of  use  as  a  working  hypothesis  in  the  further  investi- 
gation of  evolution,  nor  any  logical  ground  for  observation 
and  induction  in  nature.  The  neo-Darwinian  situation, 
and,  also,  the  neo-Lamarckian  are  in  reality  two  of  those 
common  developments  which  arise  in  every  line  of  human 
thought — intellectual  culs-de-sac . 

More  as  a  protest  against  the  neo-Darwinian  situation 
than  for  any  other  reason,  there  arose,  simultaneously,  in 
England,  on  the  Continent,  and  in  America,  the  modern 
saltationist  school.  Thoroughly  bored  with  the  repetition 
by  the  neo-Darwinians  of  the  same  old  facts  sung  to  the 
same  old  tune,  Bateson  in  England,  DeVries  on  the  Conti- 
nent, and  others,  determined  to  find  an  outlet,  and  all,  I 
think,  obtained  their  original  inspiration  from  the  recog- 
nition by  Darwin  that  in  many  species  variations  repeatedly 
occur  which  stand  apart  from  the  rest  of  the  population,  and 
frequently  are  prepotent  when  bred  back  to  the  parent 
stock.  Further,  Darwin  in  his  Origin  of  Species  and  The 
Variations  of  Animals  and  Plants  under  Domestication  cites 


170  Heredity  and  Eugenics 

many  instances  in  which  there  is  good  reason  for  believing 
that  domesticated  varieties  of  pigeons,  birds,  and  cattle, 
and  many  plants,  have  arisen  by  the  sporting  process. 

Most  biologists  have  'insisted  upon  retaining  that 
cherished  dogmatism  of  the  seventeenth  and  eighteenth 
centuries  that  there  must  be  discontinuity  between  species, 
and  the  idea  seemed  plausible  that  if  discontinuity  existed 
between  species  when  they  were  finished,  there  was  no 
a-priori  reason  why  it  could  not  have  arisen  at  the  start. 
Therefore,  Bateson,  in  the  latter  part  of  the  nineteenth 
century,  gathered  what  data  existed  in  the  literature  on 
sports  and  discontinuous  variations,  in  the  effort  to  find  an 
outlet  from  the  cul-de-sac  into  which  neo-Darwinianism 
had  led  English  biologists. 

At  about  the  same  time  DeVries  in  Holland  became 
convinced  from  a  somewhat  different  point  of  view  that  a 
similar  process  must  be  operative  in  the  production  of 
species  in  nature.  DeVries  sought,  therefore,  to  find  in 
nature  plants  which  exhibited  the  kind  of  variation  that 
he  conceived  of  as  being  the  basis  of  transmutation,  and 
finally  discovered  that  Oenothera  Lamarckiana  seemed  to 
be  undergoing  exactly  the  sort  of  process  which  he  hoped 
to  find. 

Others  became  convinced  that  there  were  possibilities 
in  this  direction,  and  as  a  result  there  is  at  present  a  well- 
developed  school  of  saltationists  whose  central  idea  is 
that  progressive  and  efficient  steps  in  transmutation  take 
place  through  sudden,  steplike  variations,  producing,  as 
DeVries  asserts,  something  quite  new  each  time. 

Directly  associated  with  the  development  of  this  idea, 
and  contributing  much  to  its  development,  was  the  redis- 
covery of  Mendel's  paper  on  the  "Behavior  of  Hybrid 


Modification  of  Germinal  Constitution  of  Organisms       171 

Peas,"  which  gave  impetus  to  investigations  that  strength- 
ened and  extended  the  saltationist  conception. 

It  would  be  rash  indeed  to  deny  that  there  are  "sports" 
in  the  Darwinian  sense,  and  DeVries'  "mutations"  are 
asserted  by  some  to  be  but  the  same  kind  of  variations 
with  a  new  name,  but  the  fact  of  the  occurrence  of  sudden 
variations  is  established  beyond  doubt.  However,  next 
to  nothing  is  known  concerning  the  rise  and  behavior  of 
these  sports  and  the  part  they  play  in  the  transmutation  of 
organisms  hi  nature,  and  it  may  be  wisest  to  suspend  judg- 
ment as  to  the  relative  importance  of  saltation  as  a  method 
of  evolution.  The  saltation  conception,  however,  considered 
in  its  broadest  sense,  has  decided  advantages  over  the  neo- 
Darwinian  and  neo-Lamarckian  positions,  because  it  is 
directly  open  to  experimental  study  and  does  serve  as  a 
fairly  logical  and  workable  hypothesis  for  investigation.  In 
its  broadest  aspects  it  is  in  no  way  like  Weismann's  theory, 
although  DeVries  has  endeavored  to  give  it  a  position  not 
unlike  that  of  germinal  selection  by  placing  all  essential 
processes  in  the  hypothetical  pangenes.  Out  of  this  situa- 
tion perhaps  the  greatest  advance  that  has  been  produced 
is  the  revival  of  interest  in  bionomic  investigations  and  the 
clearing  of  the  mist  from  many  questions,  even  though  the 
questions  have  not  been  fully  answered.  Regardless  of  what 
the  future  may  have  in  store,  the  saltationist  school  has 
rendered  biology  a  very  real  and  lasting  service  in  arousing 
new  enthusiasm  for  the  experimental  study  of  evolution 
problems  and  in  breaking  away  from  neo-Darwinianism, 
neo-Lamarckianism,  and  orthogenesis,  whose  deadly  chants 
were  slowly  but  surely  lulling  into  complacent  inactivity  the 
greatest  heritage  from  Darwin — the  experimental  study  of 
evolution  problems. 


172  Heredity  and  Eugenics 

The  saltationist  school,  aside  from  a  considerable  num- 
ber of  clearly  formulated  questions,  has  very  clearly  raised 
the  issue  as  to  whether  changes  in  the  constitution  of  the 
germinal  material  are  accomplished  by  the  slow  quantita- 
tive accumulation  of  useful  variations,  or  take  place  by 
sudden  steps,  appearing  with  discontinuity  in  the  end  result. 
Much  experience  with  this  method  of  quantitative  accumula- 
tion had  given  adequate  reason  to  distrust  it  as  a  particularly 
potent  means  of  inducing  experimental  change,  and  refuge 
not  infrequently  had  been  sought  in  the  soul-satisfying 
myths  of  germinal  selection,  orthogenesis,  isolation,  growth 
force,  bathmic  force,  and  many  other  intricately  contrived 
and  all  inclusive  hypotheses,  but  all  were  found  utterly 
useless  for  actual  experimental  investigation  and  analysis, 
such  as  is  demanded  in  physical  and  chemical  science. 

In  seeking  for  an  outlet  from  the  culs-de-sac  of  evolu- 
tionary science  as  it  existed  in  the  last  quarter  of  the  nine- 
teenth century,  DeVries  concluded  that  change,  per  saltum, 
was  quite  as  liable  to  be  a  real  method  of  transmutation  and 
sought  to  put  it  to  a  test  by  seeking  in  nature  for  species 
of  plants  that  were  undergoing  this  kind  of  change  if  such 
existed.  Darwin  had  already  noted  the  frequent  occurrence 
of  large  sudden  departures  in  both  plants  and  animals,  but 
was  of  the  opinion  that  both  large,  sudden,  and  small 
fluctuations  were  operative  in  transmutation  phenomena. 

The  discovery  of  O.  Lamarckiana  (Fig.  62)  in  an 
abandoned  field  near  Hilversum  in  Holland,  into  which 
it  had  escaped  from  a  near-by  park,  provided  most  favor- 
able material  for  DeVries'  further  study.  Here  it  grew  in 
quantity  with  two  apparently  newly  arisen  derivative  forms, 
0.  laevifolia  and  O.  brevistylis.  Plants  from  this  waste 
land  were  taken  into  the  botanic  gardens  of  Amsterdam 


Modification  of  Germinal  Constitution  of  Organisms      173 


FIG.  62. — Oenothera  Lamarckiana,  the  original  type  of  plant  used  by  DeVries 
in  his  experiments.  This  is  the  stock  from  Hilversum,  from  which  arose  in  suc- 
cessive generations  a  series  of  new  forms  by  sudden  jumps.  From  DeVries. 


174  Heredity  and  Eugenics 

and  there  gave  rise  to  several  new  types  during  the  years 
of  DeVries'  observation.  Some  of  these  arose  in  the 
experiments  but  once,  as  for  example,  0.  gigas  (Fig.  63), 
a  tall,  robust  form  with  large  flower,  the  finest  of  all  the  new 
types.  It  appeared  in  1895  and  was  one  out  of  about  14,000 
plants,  but  was  not  the  only  new  type  to  appear  in  the  crop 
of  that  year.  Six  others  were  found:  0.  albida,  of  which 
there  were  fifteen  examples  (Fig.  64);  0.  oblonga  (Fig.  65), 
of  which  176  specimens  appeared;  O.  rubrinervis,  eight 
specimens;  0.  scintillans  (Fig.  66),  one  specimen.  This 
year  gave  the  greatest  number  of  new  forms  of  any,  although 
other  years  (1896,  1897)  gave  all  but  the  0.  gigas. 

A  good  idea  of  the  real  differences  existing  between 
these  derivative  forms  and  the  parent  plants  is  given  in 
Fig.  67,  where  the  plants  are  shown  growing  side  by  side. 

In  Fig.  68  is  given  in  condensed  form  the  line  of  descent 
and  the  appearance  of  the  derivative  forms  from  year  to 
year. 

If  all  be  granted  that  is  claimed  for  the  separateness  of 
these  types,  and  admitting  also  that  they  are  absolutely 
constant  in  type  and  in  heredity,  there  still  remains  one 
striking  difference  between  these  DeVriesian  "mutations" 
and  the  "sports,"  "saltations,"  etc.,  of  other  writers: 
namely,  the  mutations  occurred  in  numbers  in  every  genera- 
tion for  a  considerable  period,  through  several  consecu- 
tive generations;  the  sports  of  Darwin  appear  but  once, 
rarely,  and  not  successively.  Upon  the  curious  findings 
in  0.  Lamarckiana,  DeVries  has  built  the  hypothesis  of 
a  premutation  period  in  which  the  germ  plasm  was 
elaborating  new  pangenes  which,  when  the  pangenes  reached 
a  certain  point,  broke  out  into  visible  manifestation  as 
mutants,  and  he  further  supposed  that  after  a  time  the  new 


Modification  of  Germinal  Constitution  of  Organisms       175 


FIG.  63. — Oenothera  gigas,  a  mutant  of  Oenothera  Lamarckiana.  This  form 
arose  but  once  in  DeVries'  cultures  (in  1895),  out  of  a  culture  of  14,000  seedlings. 
From  it  has  arisen  a  strong  race  now  cultivated  in  many  gardens  in  Europe  and 
America. 


176 


Heredity  and  Eugenics 


FIG.  64. — Oenothera  albida.    Another  type  which  has  arisen  from  Oenothera 
Lamarckiana,  occurring  with  considerable  frequency  in  successive  years. 


Modification  of  Germinal  Constitution  of  Organisms      177 


FIG.   65. — Oenothera   oblonga.    A   type  which  has  arisen   from    Oenothera 
Lamarckiana. 


I78 


Heredity  and  Eugenics 


FIG.  66. — Oenothera  scintillans.    A  rather  rare  mutant  of  Oenoihera  Lamarck- 


Modification  of  Germinal  Constitution  of  Organisms      1 79 


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Heredity  and  Eugenics 


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Mutants  anu  Number  observed  in          O.Lamarck-      Mutants  and  Number 
different  years  tana          observed  in  different  years 

The  mu- 
tating 
stem  form 

FIG.  68. — Diagram  showing  in  condensed  form  the  genealogy  of  the  Oenothera 
Lamarckiana  family  and  its  various  mutants  during  successive  years.  The  num- 
bers under  each  type  represent  the  number  of  new  types  observed  in  each  year. 


As  far  as  causes  were  concerned,  DeVries  had  little  to  offer 
except  the  suggestion  that  the  cause  was  ultimately  probably 
an  external  one. 


Modification  of  Germinal  Constitution  of  Organisms       181 

There  is  not  the  least  doubt  as  to  the  behavior  of  0. 
Lamarckiana  and  the  appearance  of  the  "mutants,"  and  it 
appeared  to  many  that  there  was  a  good  chance  of  producing 
"mutating  races"  by  external  forces  acting  upon  the  germ 
of  the  parent  race.  The  last  decade  has  produced  a  deal 
of  evidence  that  external  forces  can  produce  germinal 
changes,  but  these  are  in  all  instances  immediate  and  final. 
New,  divergent  types,  more  or  less  separated  from  the 
parent,  have  appeared,  but  in  none  are  there  subsequent 
mutations. 

I  had  been  at  work  upon  this  problem  and  had  found 
and  reared  sports  of  Leptinotarsa  decemlineata  as  early  as 
1893,  and  on  the  appearance  of  DeVries'  work  I  began  in  a 
systematic  way  to  try  to  produce  mutating  races  by  the 
use  of  external  forces.  I  have  thus  far  positively  failed  to 
produce  a  mutating  race  by  these  agencies,  although  I  have 
been  able  to  get  changes  in  profusion,  some  of  which  I  shall 
describe  later. 

In  1901  I  tried  to  produce  a  mutating  race  by  crossing 
L.  decemlineata,  L.  juncta,  and  L.  pallida,  with  the  idea 
that  perhaps  the  interbreeding  and  combination  of  the 
chief  characters  of  the  three  into  a  hybrid  complex  would 
produce  a  type  which  under  changed  conditions  of 
growth  and  development,  or  of  changed  or  adverse 
environment,  would  give  the  mutation  behavior  of  O. 
Lamarckiana.  The  early  experiments  were  just  beginning 
to  show  promise  of  interesting  results  when  they  were 
brought  to  an  end.  As  subsequent  results  have  shown,  this 
was  a  good  working  hypothesis  but  these  first  experiments 
would  not  have  led  to  the  results  wanted.  In  1902  Bateson 
suggested  that  the  mutation  phenomena  in  Oenothera  was 
possibly  akin  to  a  Mendelian  splitting  of  a  hybrid  type. 


1 82  Heredity  and  Eugenics 

From  the  year  1904  onward  I  have  been  able  to  carry 
out  a  number  of  suggestive  experiments  in  the  further  effort 
to  produce  a  mutating  race  experimentally. 


EXPERIMENTS  IN  THE  SYNTHESIS  OF  A  MUTATING  STEM  RACE 

An  extensive  set  of  these  experiments  has  been  in 
progress  for  some  years,  some  of  which  have  now  developed 
far  enough  to  allow  of  rather  definite  statements.  The 
method  employed  has  been  to  take  species  derived  from 
nature  from  some  restricted  locality,  to  keep  close  watch 
upon  what  goes  on  in  this  locality,  and  also  to  analyze  the 
composition  of  the  species  from  this  locality  by  cultures  in 
the  laboratory.  In  this  way,  stocks  of  known  character  are 
obtained  from  experiment,  and  also  natural  stocks  whose 
attributes  are  well  known  are  developed  in  the  type  localities. 
In  the  experiments  in  synthesis  either  pedigreed  stocks  from 
the  laboratory,  or  the  stocks  from  nature,  or  both,  are 
placed  in  nature  upon  their  food  plant  in  isolated  localities, 
or  in  large  cages,  and  allowed  to  breed  as  if  the  introduction 
were  a  natural  one. 

In  1904,  an  isolated  area  of  about  an  acre  upon  the 
southern  slope  of  a  barranca,  near  Cuernavaca,  was  planted 
with  food  plants,  upon  which  both  L.  signaticollis  and  L. 
undecimlineata  would  feed.  In  July,  1904,  this  spot  was 
stocked  with  a  culture  of  210  specimens  of  L.  signaticollis, 
from  a  standard  location  about  a  mile  and  a  half  distant, 
and  354  specimens  of  L.  undecimlineata,  obtained  at  El  Hule, 
on  the  banks  of  the  Rio  Papaloapan.  The  groups  were 
equally  divided  between  the  sexes,  were  young  and  vigor- 
ous, immediately  began  breeding,  and  intercrossed  freely. 
Under  experimental  conditions  these  forms  cross  freely  in 


Modification  of  Germinal  Constitution  of  Organisms       183 

both  directions,  but  out  of  them  no  new  characters  come 
as  the  result  of  ordinary  crossing. 

In  the  first  generation  of  this  colony  there  was  an 
abundance  of  individuals  of  both  sexes  of  the  signaticollis 
type,  and  of  the  undecimlineata  type,  and  of  a  highly 
variable  intermediate  hybrid  type.  A  census  was  made  of 
the  population  on  August  14  to  1 7,  with  the  following  results : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

4,5l8  11,744  5,091 

In  this  experiment,  it  was,  of  course,  impossible  to  tell 
from  inspection  whether  the  signaticollis  individuals  were 
pure  signaticollis,  or  pure  signaticollis  and  a  hybrid  with  the 
signaticollis  dominant,  and  the  same  was  true  with  respect 
to  the  undecimlineata.  All  of  the  beetles  entered  into 
hibernation  during  the  latter  part  of  August  and  early  in 
September,  1904.  The  food  plants  survived  the  long,  hard, 
dry  season  and  came  up  in  the  spring  of  1905  in  abundance, 
and  in  June,  1905,  individuals  of  all  three  types  emerged 
and  were  found  to  be  interbreeding  freely.  A  census  made 
of  the  individuals  which  emerged  late  in  June  gave  the 
following  results : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

1,027  i,744  478 

which  clearly  indicate  that  through  some  cause  the  hiber- 
nating conditions  of  the  location  were  favorable  for  signati- 
collis, but  decidedly  unfavorable  for  the  undecimlineata 
and  for  the  intermediate  hybrid  type.  These  individuals 
were  allowed  to  interbreed  freely  and  produced  a  numerous 
progeny,  in  which  the  larvae  were  of  four  different  types: 
white  without  spots,  white  with  spots,  yellow  without 
spots,  yellow  with  spots.  The  second  generation  emerged 
from  the  middle  to  the  end  of  July,  1905,  and  showed  a 


184  Heredity  and  Eugenics 

huge  preponderance  of  the  signaticollis  type.  The  census 
of  a  random  sample  taken  the  last  week  in  July  gave  the 
following  count : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

1,244  1,192  367 

These  individuals  were  not  removed  from  the  colony; 
the  census  of  the  sample  was  made,  the  individuals  put 
back,  and  the  colony  allowed  to  encounter  the  conditions 
and  behavior  which  it  would  meet  in  a  state  of  nature. 
Nine  pairs,  taken  at  random,  of  the  undecimlineata  type 
were  bred  out  as  pedigreed  cultures  during  August  and 
part  of  September,  1905,  and  gave  uniformly  an  undecim- 
lineata progeny.  Seven  pairs  of  the  signaticollis  type, 
which  were  bred  out,  gave  uniformly  a  signaticollis  progeny, 
and  out  of  five  other  pairs  there  appeared  individuals  of  the 
mid-type  and  of  the  undecimlineata  type,  showing  that 
some  of  the  signaticollis  type  were  hybrid  in  character. 
Six  pairs  of  the  mid-type  were  also  bred  out  as  pedigreed 
stock,  and  showed  themselves  to  be  in  every  case  hybrid. 
The  third  generation  was  produced  in  August  and  early 
September,  1905.  In  this  the  larvae  were  of  the  same 
four  classes,  but  showed  a  huge  preponderance  of  yellow 
larvae  (ylS).  A  count  made  late  in  August,  when  perhaps 
the  bulk  of  the  larvae  had  entered  into  pupation,  gave  the 
following  results : 

Whs  WhS  ylS  Yls 

205  227  849  321 

The  adults  of  Generation  III  emerged  early  in  September; 
a  census  made  about  the  middle  of  September  gave  the 
following : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

2,452  827  218 


Modification  of  Germinal  Constitution  of  Organisms      185 

showing  again  a  marked  decrease  in  the  undecimlineata 
form,  a  lesser  decrease  in  the  intermediate  hybrid  type,  and 
a  much  greater  relative  increase  in  the  signaticollis  type. 
These  hibernated  during  the  winter  of  1905-6  and  emerged 
in  June,  1906.  They  were  allowed  to  interbreed  freely. 
The  population  was  not  seen  at  the  time  of  emergence, 
but  in  the  fourth  generation  it  was  observed  in  July,  1906, 
and  the  undecimlineata  type  and  the  mid-type  were  nearly 
absent.  The  census  made  at  this  time,  when  the  first 
generation  of  the  year  was  apparently  at  its  height,  gave  the 
following  results : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

3,275  45  7 

These  then  inbred  and  the  colony  was  next  seen  in  Septem- 
ber at  about  the  middle  of  the  month,  when  the  census  of  the 
individuals  in  the  colony  was  as  follows  in  Generation  V: 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

1,823  6  o 

These  hibernated  during  the  winter  of  1906-7  and  emerged 
in  June,  1907,  reproduced  at  once,  and  gave  an  abundant 
progeny  which  emerged  as  Generation  VI  between  the  zoth 
and  25th  of  July.  These  when  seriated  gave  the  following 
results : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

2,255  2  O 

The  second  generation  of  1907  emerged  late  in  August 
and  early  in  September,  and  of  this  generation  the  undecim- 
lineata type  was  entirely  absent,  and  the  mid-type  prac- 
tically so.  These  hibernated  and  when  seen  in  the  spring 
of  1908  only  the  signaticollis  type  emerged.  Both  genera- 
tions of  1908  and  both  generations  of  1909  have  developed 
the  presence  of  the  signaticollis  type  only. 


1 86  Heredity  and  Eugenics 

In  1908  individuals  from  this  location  were  brought  to 
Chicago  and  carried  as  pedigreed  cultures  in  the  labora- 
tory. They  have  shown  a  complete  gametic  purity  as  far 
as  could  be  determined  and  none  have  been  detected  which 
were  hybrid  in  character.  In  this  colony,  isolated  in  its 
location,  through  some  process  or  other  in  hybridization 
or  perhaps  by  selective  factors,  signaticollis  has  completely 
subjected  and  eliminated  undecimlineata.  Inasmuch  as 
L.  undecimlineata,  when  protected  from  crossing,  lives 
well  at  Cuernavaca,  and  the  selective  action  is  very  low, 
I  am  of  the  opinion  that  the  swamping  of  undecimlineata 
is  due  to  some  process  of  hybridization.  This  opinion  is 
fully  justified  by  experiments  conducted  in  cages  which 
eliminate  selective  factors. 

Another  experiment  was  begun  in  1905,  when  one 
hundred  individuals  were  taken  from  the  standard  colony 
of  L.  signaticollis  at  Cuernavaca,  and,  with  an  equal  num- 
ber of  L.  undecimlineata,  from  El  Hule,  were  planted  upon 
a  vigorous  growth  of  their  food  plants  in  a  clearing  made  in 
the  Foot  Hill  Rain  Forest,  in  the  Paraiso  district,  not  far 
from  Ojos  de  Agua,  in  the  Canton  of  Zongolica.  They  were 
observed  to  intercross  freely,  but  there  was  a  preponderance 
of  undecimlineata-like  forms,  with  a  few  intermediates, 
and  only  small  numbers  of  the  signaticollis  type  in  the  first 
generation.  The  census  made  of  the  first  hybrid  generation 
was  as  follows : 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

°  56  1,342 

A  third  generation  was  produced  in  late  November,  and 
in  that  generation  there  were  no  signaticollis  forms  visible; 
there  were  only  a  few  of  the  hybrid  intermediate  type,  and 


Modification  of  Germinal  Constitution  of  Organisms       187 

these  all  closely   approximated  the  undecimlineata  form 
The  census  obtained  late  in  November  was: 

Signaticollis  Type  Mid-Type  Undecimlineata  Type 

o  ii  1,132 

In  1906,  1907,  and  1908  these  cultures  were  allowed  to 
shift  for  themselves,  and  the  food  plants  were  nearly 
swamped  by  the  immigration  into  the  glade  of  plants  from 
the  surrounding  rain  forest;  in  fact,  the  whole  culture  was 
allowed  to  engage  in  a  most  desperate  struggle  for  its 
existence.  As  far  as  the  beetles  were  concerned,  this  was 
simply  a  struggle  for  food.  In  1908-9  the  inroads  which 
had  been  made  by  other  plants  had  so  reduced  the  number 
of  Solanums  that  the  food  supply  was  inadequate.  During 
these  years,  however,  no  trace  of  the  signaticollis  type  had 
ever  appeared.  In  1908,  material  of  the  undecimlineata 
type  was  taken  from  this  culture  to  Chicago,  and  there 
subjected  to  the  tests  of  pedigree  analysis,  but  without 
any  trace  of  the  signaticollis  form  appearing.  In  both 
experiments,  however,  at  Praesidio  and  at  Cuernavaca, 
the  resulting  materials  were  different  in  gametic  make- 
up from  the  original  species.  Superficially,  these  stocks 
could  not  be  told  from  the  natural  species,  but  when  used 
as  the  basis  of  experiment  under  control  conditions,  it  was 
found  that  there  'resulted  a  difference  in  the  behavior  of 
the  subsequent  hybrid  generations,  clearly  indicating  a 
change  in  the  gametic  constitution  of  these  groups  of 
individuals. 

A  series  of  experiments,  more  conclusive  and  under 
better  conditions,  has  been  carried  on,  using  three  species: 
L.  decemlineata,  L.  oblongata,  and  L.  multitaeniata.  Of 
these,  in  nature,  L.  decemlineata  is  limited  solely  to  the 


1 88  Heredity  and  Eugenics 

United  States  and  southern  Canada;  L.  multitaeniata 
entirely  to  the  southern  portion  of  the  plateau  of  Mexico, 
and  L.  oblongata  to  the  Balsas  Valley  and  the  Oaxaca- 
Guerrero  Highlands.  These  species  intercross  freely  under 
experimental  conditions  and  represent  the  following  con- 
trasting characters  for  consideration.  The  general  ground 
color  of  the  larvae  of  L.  decemlineata  is  wine  red,  that  of 
L.  oblongata  and  L.  multitaeniata  chrome  yellow.  L.  decem- 
lineata and  L.  multitaeniata  have  two  rows  of  spots 
along  the  side  in  the  larvae,  while  L.  oblongata  has  one. 
L.  oblongata,  as  shown  in  Fig.  60,  is  long  and  oval  in  outline ; 
L.  decemlineata,  as  shown  in  Fig.  69,  is  more  rounded; 
and  L.  multitaeniata  is  robust  in  type.  There  are  also  color 
differences  between  the  species,  which  need  not  concern  us 
here.  Three  experiments  will  serve  to  illustrate  the  pur- 
pose of  this  paper. 

In  1905,  twenty  L.  decemlineata,  from  a  pedigreed  cul- 
ture, from  Chicago,  twenty  L.  oblongata,  from  a  pedigreed 
culture  at  Cuernavaca,  and  twenty  L.  multitaeniata,  derived 
from  an  isolated  standard  locality  in  the  valley  of  Mexico 
south  of  Guadalupe,  were  placed  on  an  isolated  island  in  the 
Balsas  River.  This  island  was  fairly  well  covered  with  a 
growth  of  Solanum  rostratum,  or  a  closely  related  form,  upon 
which  all  three  species  would  feed.  As  far  as  could  be 
discovered,  the  island  was  devoid  of  any  individuals  of  L. 
oblongata,  which  occur  very  sparingly  in  that  general  region, 
and  the  neighboring  banks  of  the  river  and  the  islands  were 
all  searched,  but  they  afforded  no  trace  of  L.  oblongata. 
These  introduced  beetles  were  allowed  to  breed  and  gave 
the  first  hybrid  generation  in  August,  1905.  In  this 
generation  only  the  adults  were  seen  and  of  the  adults  we 
could  recognize  definitely  five  forms :  (A)  Those  which  on 


Modification  of  Germinal  Constitution  of  Organisms      189 

inspection  appeared  to  be  wholly  L.  decemlineata;  (B)  those 
which  appeared  to  be  wholly  L.  oblongata;  and  (C)  those 
which  appeared  to  be  wholly  L.  multitaeniata.  There  were 
individuals  which  were  manifestly  intermediate  hybrids,  in 


FIG.  69. — Arranged  to  show  some  of  the  essential  differences  between  the 
species:  L.  oblongata,  L.  multitaeniata,  and  L.  decemlineata.  (A)  Showing  the 
form  and  characteristic  markings  of  the  adult  of  L.  oblongata.  (B)  Adult  of  L. 
multitaeniata,  showing  the  more  robust  form  and  somewhat  different  type  of 
general  color  pattern  sharply  distinguishing  it  from  both  of  the  other  species.  The 
elytral  ground  color  is  often  dark  ochre,  sometimes  even  reddish.  (C)  The  type 
of  L.  decemlineata  used  in  these  experiments,  somewhat  intermediate  between  the 
two  other  species  in  body  form,  and  to  a  certain  extent  in  markings.  (D)  Showing 
the  side  view  of  a  full-grown  larva,  with  its  color  pattern.  The  ground  color  is 
yellow  and  that  of  the  adult  somewhat  variable.  (E)  Adult  larva  of  L.  multi- 
taeniata, with  the  characteristic  color  pattern.  Ground  color  is  yellow  as  in  L. 
oblongata,  but  darker.  (F)  Shows  the  characteristic  color  pattern  of  L.  decem- 
lineata; the  ground  color  of  the  larvae  is  wine  red. 

form,  punctation,  and  coloration,  between  L.  decemlineata 
and  L.  oblongata  (D) ;  and  between  L.  decemlineata  and  L. 
multitaeniata  (E).  Of  these  five  forms  a  census  was  made 
with  the  following  results: 

A  B  C  D  E 

327  371  142  1,439  246 


i  go  Heredity  and  Eugenics 

All  the  individuals  were  allowed  to  remain  in  the  colony,  and 
interbred  freely  in  August,  giving  early  in  September  a  second 
generation,  of  which  the  following  census  was  made : 

A  B  C  D  E 

46  IOI  QO  I,2Q2  2IO 

These  hibernated  during  the  winter  of  1905-6,  and  were  not 
seen  again  until  September,  1906,  in  the  fourth  hybrid 
generation  of  the  culture.  At  this  time  the  dominant  form 
was  manifestly  a  combination  between  L.  decemlineata, 
L.  oblongata,  and  L.  multitaeniata,  with  the  oblongata- 
decemlineata  attributes  in  excess  of  those  of  L.  multitaeniata 
(a  combination  between  classes  D  and  E  of  F1  and  F2) : 

A  B  C  D  E 

7  25  12  2,2IO 

The  huge  preponderance  of  this  complex  type,  which 
was  neither  one  nor  the  other  of  the  three  species,  suggests 
at  once,  of  course,  that  the  results  could  not  be  due  to  any 
selective  process,  because  the  type  was  not  one  of  the 
original  types  but  a  hybrid  complex. 

The  wintering  conditions  of  1906-7  were  especially 
rigorous,  at  least  as  judged  by  the  number  of  beetles  that  I 
found  in  that  location  in  1906-7,  when  the  following  census 
was  made: 

A  B  C  D  E 

004  422 

This  shows  that  during  the  winter  practically  only  the 
hybrid  combination  was  able  to  survive.  These  repro- 
duced and  gave  a  progeny  in  July,  1907.  An  inspection 
was  made  early  in  August,  when  I  found  only  the  dominant 
type  present  in  the  fifth  hybrid  generation. 

A  B  C  D  E 

ooo  1,877 

The  culture  was  not  seen  again  until  the  spring  of  1908, 
when  a  considerable  number  of  the  dominant  form  of  the 


Modification  of  Germinal  Constitution  of  Organisms       191 

sixth  hybrid  generation  was  found  emerging.  These  were 
taken  to  Chicago  and  subjected  to  analytical  experiments  and 
were  found  to  breed  true,  both  in  group  and  in  pedigreed  cul- 
tures, with  this  exception,  that  in  both  the  pedigreed  cultures 
there  occurred  from  time  to  time  sporadic  variants  often 
standing  a  considerable  distance  apart  from  the  rest  of  the 
population,  which,  when  inbred,  either  with  sports  like 
themselves,  or  back  to  the  parent  type,  gave  behaviors  which 
in  every  way  are  comparable  to  the  behavior  observed  in 
many  of  the  forms  which  are  supposed  to  have  arisen  by  a 
mutative  process.  These  strains  were  kept  through  the 
years  1908  and  1909,  and  gave  results  which  strongly 
suggest  that  the  interpretation  of  a  mutative  period  as 
described  by  DeVries  in  O.  Lamarckiana,  may  well  be  the 
variability  which  follows  complex  processes  of  hybridization. 

In  1906  operations  were  begun  at  Orizaba,  and  in  May 
the  same  three  species  from  the  same  original  stocks  were 
mated.  Conditions  at  Orizaba  are  decidedly  different  from 
those  in  the  Balsas  VaUey.  The  city  is  2,000  ft.  higher  in 
altitude  and  the  climate  is  very  different.  In  the  Balsas 
Valley  during  the  summer  the  days  are  bright  and  hot, 
with  even  showers.  At  Orizaba,  in  the  location  chosen 
at  the  foot  of  the  Sierra  Escamela,  it  is  never  above  90° 
even  on  the  hottest  days,  and  the  nights  are  always  cool, 
owing  to  the  downward  draught  of  cool  air  from  the  moun- 
tains which  flows  over  the  valley  at  night.  The  relative 
humidity  is  high  at  all  times,  and  the  precipitation  during 
the  season  was  74  inches. 

Under  these  conditions  the  crosses  which  were  made 
thrived  as  far  as  certain  members  were  concerned:  the 
L.  multitaeniata  individuals  were  decidedly  reduced  by  the 
conditions  under  which  they  were  living  and  the  L.  oblongata 
individuals  were  hampered  considerably,  but  to  a  lesser 


192  Heredity  and  Eugenics 

degree.  Crossing  was  observed,  however,  among  the  com- 
ponent species  in  all  directions,  and  progeny  emerged  in 
July,  showing  a  combination  to  have  been  formed  between 
L.  oblongata  and  L.  decemlineata,  with  the  L.  multitaeniata 
type  and  attributes  wanting.  The  population,  when 
examined,  showed  individuals  which  were  apparently  domi- 
nated by  L.  decemlineata  (A)  to  the  exclusion  (as  far  as 
visible)  of  all  others;  individuals  which  were  very  clearly 
intermediate  between  L.  decemlineata  and  L.  oblongata  (B) ; 
and  individuals  which  were  more  or  less  intermediate  between 
L.  decemlineata  and  L.  multitaeniata  (C).  Of  these  the 
intermediate  between  L.  decemlineata  and  L.  oblongata 
existed  in  by  far  the  greatest  numbers,  as  shown  by  the 
following  proportion: 

ABC 

131  397  92 

Inasmuch  as  this  experiment  was  conducted  in  a  large 
cage  and  not  in  the  open,  it  was  manifestly  impossible  to 
utilize  all  the  individuals  which  emerged,  so  a  reduction  was 
made  for  the  ma  tings  for  F2,  excepting  that  any  extreme 
or  rare  types  were  given  every  advantage  over  the  more 
common  types.  The  following  materials  were  selected  at 
random  from  the  different  groups  as  parents  of  the  second 
generation : 

ABC 

3*  3&  3<S 

3?  3?  3? 

These  inbred  rapidly  during  July  and  at  the  end  of  August 
gave  a  second  generation  which  was  uniformly  an  inter- 
mediate between  L.  decemlineata  and  L.  oblongata. 
ABC 

o  589  o 


Modification  of  Germinal  Constitution  of  Organisms      193 

This  was  especially  true  of  the  adult  characters.  The 
larval  characters,  however,  were  also  variable  and  appeared 
to  be  less  blended  into  a  homogeneous  group. 

The  culture  hibernated  from  early  September,  1906, 
to  June,  1907.  During  this  period  a  very  great  mortality 
occurred,  which  was  due  very  largely,  I  think,  to  the  fact 
that  the  culture  would  probably  have  reproduced  a  third 
time  in  1906  if  it  had  been  supplied  with  food  and  proper 
conditions. 

These  individuals  in  1907  reproduced  and  gave  a  pretty 
uniform  progeny  of  the  blended  type  between  L.  decemli- 
neata  and  L.  oblongata,  Generation  III: 

ABC 

2  476  o 

A  fourth  generation  was  obtained  hi  late  August  and  early 
September  of  the  same  year,  which  possessed  the  same 
attributes  as  the  third  generation.  In  nature,  this  culture 
was  not  carried  beyond  that  stage,  but  material  from  the  cul- 
ture was  brought  to  Chicago  and  carried  through  the  winters 
of  1907  and  1908,  and  the  summer  of  1908  and  part  of  1909. 
It  was  subjected  to  various  analytical  experiments,  all  of 
which  tended  to  show  that  the  type  was  a  relatively  stable 
one.  Individual  pairs,  when  inbred,  gave  a  very  definite 
pure  line  culture  and  groups  mated  at  random  gave  the 
same  result;  but,  as  in  the  colony  in  the  Balsas  River,  there 
appeared  sporadic  individuals,  widely  separated  from  the 
parent  stock,  which,  when  inbred,  behaved  in  every  way 
like  DeVries'  mutants. 

A  culture  of  the  same  material  was  placed  at  the  Desert 
Botanical  Laboratory  of  the  Carnegie  Institution  in  the 
desert  of  southern  Arizona  at  Tucson,  near  the  foot  of 
Tumamoc  Hill.  In  this  experiment  two  males  and  two 


i94  Heredity  and  Eugenics 

females  of  L.  decemlineata,  from  the  typical  stock  at  Chicago, 
two  males  and  two  females  of  L.  oblongata,  and  two  males 
and  two  females  of  L.  multitaeniata  were  mated  in  the  early 
part  of  June.  This  culture  was  confined  in  a  cage  6  ft. 
square  on  the  ground  and  3  ft.  high,  covered  with  wire 
eighteen  meshes  to  the  inch,  thus  eliminating  all  selection 
by  insectivorous  enemies.  S.  rostratum  was  supplied 
as  food  in  sufficient  quantity.  During  June  and  July 
these  reproduced  abundantly  and  gave  a  large  progeny 
which  emerged  late  in  July  and  early  in  August.  In  this 
first  hybrid  generation  at  Tucson  there  was,  as  in  the  other 
cultures,  a  blending  of  the  materials  introduced  into  the 
experiment,  but  in  this  culture  L.  decemlineata  was  the 
dominant  member  of  the  cross,  although  not  completely. 
In  the  larvae  six  types  were  observed: 

1.  Those  which  on  inspection  appeared  to  be  L.  decem- 
lineata. 

2.  Those  which  were  L.  oblongata. 

3.  Those  which  were  L.  multitaeniata. 

4.  Those  which  were  intermediate  between  L.  decem- 
lineata and  L.  multitaeniata. 

5.  Those  which  were  intermediate  between  L.  decem- 
lineata and  L.  oblongata. 

6.  Those   intermediate   between   L.    oblongata   and   L. 
multitaeniata. 

It  was,  of  course,  impossible  to  tell  on  inspection  what 
the  constitution  of  each  of  these  types  was.  Five  classes 
of  adults  were  recognized: 

A)  Those  which  were  clearly  either  pure,  or  dominants 
of  the  L.  oblongata  type. 

B)  Those  which  were  clearly  intermediate  hybrids  be- 
tween L.  decemlineata  and  L.  oblongata. 


Modification  of  Germinal  Constitution  of  Organisms       195 

C)  An  L.  decemlineata  type  in  which  L.  decemlineata 
was  in  the  main  dominant,  but  which  exhibited  a  variable 
range  of  variability. 

D)  Intermediate  hybrids  between  L.  decemlineata  and 
L.  multitaeniata. 

E)  Forms  which  were  either  L.  multitaeniata  pure,  or 
heterozygotes,  in  which  L.  multitaeniata  was  completely 
dominant. 

Out  of  1,8.57  adults  seriated,  the  following  census  was 

made: 

A  B  c  D  E 

47  29  1,311  261  103 

This  census  shows  that  while  L.  decemlineata  is  either  the 
dominant  or  prepotent  member  of  the  combination,  it  did 
not  come  out  of  the  mixture  entirely  without  contamination. 
This  experiment  was  continued  in  a  cage  exactly  like 
the  first,  and  the  following  materials  were  taken  at  random 
from  the  first  generation  as  the  parents  of  Generation  II : 

A  B  C  D  E 

2$  2$  6s  3$  33 

2$  22  6?  3?  3? 

This  material  immediately  began  breeding  and  gave  during 
the  month  of  August  a  large  progeny  which  emerged  early 
in   September,   and   immediately   went   into   hibernation. 
When  seriated,  this  material  gave  the  following  results : 
A  B  c  D  E 

o  29  247  42  o 

These  passed  the  winter  of  1908-9  in  the  ground  and 
emerged  in  June,  1909.  All  that  emerged  were  allowed  to 
reproduce  in  the  cage  and  were  supplied  with  food  as  fast 
as  it  was  consumed.  These  gave  a  very  large  progeny 
which  appeared  to  be  uniformly  of  the  dominant  types  of  the 
first  and  second  generations.  Seriation  of  the  material 


196  Heredity  and  Eugenics 

obtained  from  Generation  III  at  the  end  of  August,  1909, 
gave  the  following  results: 

A  B  c  D  E 

o  5  362  8  o 

I  then  mated  at  random  for  the  parents  of  Generation 
IV,  one  male  of  B,  the  only  one  that  could  be  found  alive, 
three  males  and  three  females  of  C,  two  males  and  two 
females  of  D,  and  none  of  E,  they  being  absent.  This 
material  bred  at  once  and  gave  in  the  fourth  generation  a 
considerable  progeny,  which  were  all  of  the  dominant  type. 

Material  from  Generation  IV,  brought  to  Chicago  in 
August,  1909,  placed  in  hibernation  under  experimental 
conditions,  and  brought  out  to  breed  in  the  middle  of  the 
winter,  has  shown  that  the  dominant  type  is  a  fixed  type, 
and  that  it  breeds  true  and  does  not  split  in  subsequent 
generations.  The  only  splitting  is  that  which  occurs  in  rare 
individuals  in  from  2  to  3  per  cent  of  the  progeny,  which 
stand  apart  from  the  general  population  as  sports.  These 
cases  are  practically  the  reappearance  of  one  or  the  other  of 
the  component  characters  or  combinations  thereof  that  went 
into  the  cross,  and  they  do  not  represent  in  this  experiment 
anything  in  the  way  of  characters  new  to  the  genus  or  family 
as  DeVries  states  to  be  true  of  his  mutants,  rather  they 
are  simply  the  characters  obtained  from  the  different  parents 
from  which  this  complex  has  been  built  up. 

The  same  combination  of  material  was  made  in  Chicago 
in  1908,  and  was  run  through  essentially  the  same  pro- 
cedure as  that  of  the  Tucson  experiment,  with  this  difference 
in  the  result,  that  at  Chicago  L.  decemlineata  completely 
dominated  the  culture  to  the  total  exclusion,  as  far  as  analy- 
sis has  been  able  to  discover,  of  the  presence  of  the  other 
parents. 


Modification  of  Germinal  Constitution  of  Organisms      197 

These  experiments  in  synthesis  represent  what  might 
happen  in  a  state  of  nature  when  species  which  can  hybridize 
migrate  from  one  place  to  another  and  intercross.  No 
one  realizes  better  than  I  the  complexity  of  experiments 
of  this  kind,  the  difficulties  involved  in  the  analysis  of  the 
results,  and  the  caution  that  should  be  exercised  in  making 
statements  from  them.  It  seems  certain  from  these  experi- 
ments, as  far  as  they  have  been  carried  out,  and  they  are 
by  no  means  complete,  that  we  may  definitely  conclude 
that  when  like  materials  are  combined  under  different 
natural  environments,  differences  in  the  products,  depending 
upon  the  conditions  under  which  the  combination  takes 
place,  result.  It  is  certain  that  the  type  which  came  out  of 
the  culture  in  the  Balsas  Valley  was  quite  different  from 
that  which  resulted  from  the  cultures  at  Orizaba,  and  these 
are  different  from  the  dominant  type  which  arose  at  Tucson. 

One  point  of  very  considerable  interest  is  the  behavior  of 
these  dominant  types  in  exactly  the  way  in  which  DeVries' 
Oenothera  Lamarckiana  behaves,  giving  in  each  generation, 
a  greater  or  less  number  of  rather  divergent  individuals, 
which,  when  inbred,  are  found  to  be  stable  germinal  varia- 
tions. 

Bateson  in  1902  suggested  that  the  mutations  observed 
by  DeVries  in  Oenothera  Lamarckiana  are  in  reality  due  to 
some  sort  of  hybridization  behavior.  I  am  of  the  opinion 
that  Bateson's  suspicion  is  probably  justified,  at  least  in 
some  instances.  I  have  no  experience  with  plants,  and 
especially  none  with  O.  Lamarckiana,  but  my  experience 
with  these  synthetic  experiments  has  suggested  that  the 
type  of  behavior  which  DeVries  has  discovered,  and 
upon  which  he  has  built  an  all-inclusive  theory  of  evo- 
lution, is  in  reality  nothing  more  than  the  reappearance 


198  Heredity  and  Eugenics 

from  time  to  time  of  attributes  brought  into  the  strain  by 
hybridization,  and  which  reappear  in  every  generation,  or  in 
frequent  generations,  by  some  process  akin  to  Mendelian 
segregation. 

It  seems  unreasonable  to  advance,  as  has  DeVries,  the 
idea  of  a  premutation  period,  with  a  gradual  development 
of  invisible  pangenes,  and  then  a  final  bursting  of  these 
pangenes  into  a  full-fledged  mutation  period,  followed  by  a 
gradual  dying  away  of  the  mutation  period  which  leaves 
a  species  in  a  condition  in  which  it  does  not  produce  these 
sports.  Rather,  the  explanation  which  Bateson  suggested, 
and  which  I  have  shown  to  be  capable  of  creation  in  these 
synthetic  experiments,  is  far  more  plausible  and  more 
likely  to  be  the  real  explanation  of  the  type  of  behavior 
found. 

This  raises  a  very  large  question — one  that  has  been 
raised  many  times — as  to  whether  natural  species  may  not 
be  hybridization  complexes  rather  than  pure  line  cultures 
isolated  by  some  sort  of  selection,  as  has  been  presupposed 
since  the  time  of  Darwin.  I  have  found  that  in  nature, 
crossing,  especially  between  these  chrysomelid  beetles,  is 
by  no  means  uncommon,  and  very  frequently  results  in 
adult  progeny  in  nature,  some  of  which  have  been  described 
as  species.  These  natural  cases  of  hybridization  have 
been  observed  in  the  last  half-dozen  years  along  the  edge  of 
the  Mexican  plateau.  Some  other  species  of  chrysomelids, 
from  the  same  general  region,  especially  some  species  of 
Labidomera,  have  a  variability  strongly  suggestive  of  a 
similar  origin.  I  have  found  that  Labidomera  suturella 
Chevr.,  of  which  many  sharply  marked  variations  have 
been  described,  gives  a  variability  in  pedigreed  cultures 
that  is  strongly  suggestive  of  the  species  having  arisen 


Modification  of  Germinal  Constitution  of  Organisms      199 

through  a  process  of  hybridization.  On  the  high  volcanic 
plateau  of  Toluca  there  is  another  type  rather  closely  allied 
to  L.  multitaeniata,  which  is  also  suggestive  of  having  arisen, 
or  of  being  in  the  process  of  arising,  through  hybridization. 

These  conditions  in  nature  are  of  course  difficult  or 
impossible  to  check  and  verify,  because  the  past  is  absolutely 
unknown,  and  little  or  no  indication  of  what  it  has  been 
can  be  obtained  from  any  source.  The  materials  in  muse- 
ums and  the  records  by  systematists  are  utterly  useless  for 
this  purpose.  Apparently  the  only  way  of  attacking  this 
problem  is  the  one  which  I  have  adopted  of  placing  colonies 
in  isolated  locations,  or  in  cages,  there  to  carry  out  the 
process  of  interbreeding  and  forming  of  hybrid  combina- 
tions as  they  would  occur  in  nature. 

In  the  last  few  years  at  Tucson  a  series  of  experiments 
has  given  an  exact  duplication  of  the  "mutation  behavior," 
and  further,  it  is  clearly  called  into  operation  by  conditions 
external  to  the  organism.  At  first  a  race  was  synthetized 
and  was  and  is  still  constant,  but  when  placed  under  opti- 
mum conditions  of  growth  and  development  at  Tucson  it 
has  given  fourteen  distinct  types.  Some  of  these  had  in 
previous  experiments  been  tested  out  and  are  known  to  breed 
true,  and  others  are  still  to  be  tested. 

With  plants,  Gates  and  Davis  are  endeavoring  to  pro- 
duce synthetically  O.  Lamarckiana  from  a  hybridization  of 
O.  grandiflora  and  O.  biennis,  and  while  as  yet  0.  Lamarcki- 
ana has  not  been  produced,  Davis  has  obtained  a  type  which 
he  considers  to  be  very  close  thereto.  It  is  perhaps  not 
too  much  to  expect  that  in  the  near  future  0.  Lamarckiana 
will  be  experimentally  synthetized. 

If  it  proves  to  be  generally  true  that  "mutation  behav- 
ior" is  a  sequence  of  synthetic  composition,  it  does  not  in 


2oo  Heredity  and  Eugenics 

any  way  detract  from  the  value  of  DeVries'  observations, 
nor  of  the  role  which  types  thus  arisen  may  play  in  evolu- 
tion. It  is  true  that  the  hypothetical  portion  of  DeVries' 
theory  as  regards  a  permutation  period  and  so  on,  is  in  part 
true,  hi  part  not.  There  is  a  period  of  synthesis,  ending 
in  a  uniform  stem  race  that  may  endure  for  a  long  time,  and 
subsequently  this  throws  off  from  itself  gametes  unlike, 
in  that  there  are  new  combinations  of  old  characters, 
reappearance  of  long  latent  characters,  and  not  infrequently 
new  characters. 

There  is,  however,  this  essential  difference  between  the 
conception  of  DeVries  and  the  one  that  I  have  to  offer: 
namely,  DeVries  regards  species  as  pure  in  the  old  sense 
and  arising  by  dichotomy,  while  I  am  convinced  that  prog- 
ress will  show  that  synthetic  combinations  are  largely 
responsible  for  the  stem  forms  of  generic  groups,  and  that 
from  these  there  have  arisen  related  species  or  types  in 
greater  or  less  profusion.  As  far  as  experience  goes,  this 
production  of  new  types  is  in  the  main,  if  not  entirely,  a 
product  of  the  action  of  external  forces  upon  the  gametic 
constitution,  although  when  once  started  in  such  a  strain 
it  seems  not  to  cease  for  some  time  though  the  inciting  cause 
is  removed.  In  Fig.  70 1  have  tried  to  show  in  diagrammatic 
fashion  the  essential  differences  of  the  two  conceptions. 

B.       The    Experimental    Production    of    Germinal    Variations    by 
the  Direct  Action  of  Different  Forces 

I.  FORCES  EXTERNAL  TO  THE  ORGANISM 

Incident  solar  radiation  in  its  various  manifestations, 
the  water  relations  of  organisms,  density  and  composition 
of  the  medium,  and  the  nature  of  the  food  stream  are  the 
common  groups  of  forces  that  are  apt  to  be  modified  in 


Modification  of  Germinal  Constitution  of  Organisms       201 


Mutants  tm          Mutant* 

, ryrrn  t 

'  "    '^/  *  >•• 


Stem          Mutants 


Mutation   Behavior  as  Observed   by   DeVries   in  O.  Mutation  Behavior  as  Produced  in  Leptinotarsa  and 

Lamartkiana  and  Hi.  Hypothesis  of  Mutation  Periods  Genetico-Dynamic  Hypothesis  of  Mutation  and  Pro- 

duction  of  Mutating  Stem  Forms 

FIG.  70. — Diagram  to  show  the  differences  between  DeVries'  theory  of  the 
origin  of  mutations,  and  the  hypothesis  of  Mutation  as  a  result  of  hybrid 
synthesis  of  the  mutating  stem  form. 


202  Heredity  and  Eugenics 

presence,  character,  or  intensity,  in  relation  to  the  organisms, 
and  to  these  forces  and  relations  are  attributed  a  variable 
value  in  the  production  of  germinal  variations.  All  kinds 
of  extreme  demands  are  made  upon  external  forces,  from 
the  conception  of  an  organism  as  a  plastic  material  which  is 
pressed  into  shape,  and  given  its  characters  by  the  stress 
of  environment,  to  the  opposite  assertion  that  environ- 
ment acts,  if  at  all,  as  a  minor  factor  in  eliminating  the  unfit. 
From  logic  and  argument  no  truth  may  be  expected,  and 
the  only  hope  of  progress  in  the  quest  for  truth  in  this 
problem  lies  in  the  domain  of  exact  genetic  research. 

In  this  chapter — which  is  a  summary  of  recent  advances 
and  not  a  historical  resume  of  the  whole  subject — the  earlier 
work  is  not  discussed,  because  it  has  been  so  often  summar- 
ized that  good  discussions  of  it  are  available  in  many 
publications.  All  of  the  older  work,  however,  is  seriously 
defective  when  considered  from  the  viewpoint  of  present- 
day  genetic  investigations. 

IN  PLANTS 

In  the  bacteria  and  yeasts  the  refined  and  accurate 
methods  of  investigation  now  used,  and  the  fuller  recog- 
nition of  the  genetic  requirements  have  made  possible  studies 
which  have  given  much  valuable  information.  The  work 
of  Pringsheim,  Winogradsky,  Hansen,  Barber,  Beijerinck, 
Buchanan,  and  others  stands  as  examples  of  what  may  be 
accomplished  in  the  study  of  this  problem  in  these  simple 
organisms.  In  all  of  the  observations  thus  far  made  upon 
these  organisms  response  to  incident  forces  or  changed  con- 
ditions is  immediate,  and  departures,  often  of  considerable 
magnitude  in  form  and  function,  occur;  but  in  most  in- 
stances difficulty  in  fixing  these  modified  characters  has 
been  encountered. 


Modification  of  Germinal  Constitution  of  Organisms       203 

The  well-organized  experiments  of  Buchanan  with  Strep- 
tococcus lacticus  are  quite  characteristic  of  the  general 
results  obtained  in  the  investigation  of  this  problem  in 
unicellular  plants.  His  conclusion  that  fluctuations  cannot 
be  fixed  in  bacteria,  whether  normal  or  induced,  is  in  accord 
with  most  of  the  experiments  of  bacteriologists;  neverthe- 
less, this  result  is  opposed  by  many  records,  believed  to  be 
accurate,  of  sudden  permanent  departures  in  form  and 
function,  especially  in  the  yeasts. 

After  a  comprehensive  survey  of  these  studies  upon 
bacteria,  Pringsheim  concludes  that  while  changes  in  yeasts 
and  bacteria  have  often  resulted  from  the  unusual  action  of 
culture  media,  toxic  solutions,  temperature,  etc.,  the  modi- 
fications of  form  and  activity  are  diverse,  and  are  either 
permanent  or  transient.  Especially  difficult,  however,  if  not 
impossible  in  these  organisms,  is  the  attempt  to  separate 
somatic  and  germinal  effects,  and  much  reasonable  doubt 
exists  as  to  its  possibility.  The  important  contribution  from 
this  work  with  bacteria  and  yeasts  is  the  precise  demon- 
stration that  the  departures  are  readily  produced,  and 
are  a  direct  result  of  the  incident  external  forces  used,  even 
in  the  simplest  known  organisms. 

Other  low  plants,  such  as  algae  and  fungi,  have  often 
been  subjected  to  exciting  agencies,  and  while  changes  have 
resulted,  these,  like  the  modifications  in  bacteria,  are  usually 
transient  and  not  permanent.  It  would  seem  that  these 
simple  forms  ought  to  provide  good  material  for  the  study  of 
this  problem,  although  it  is  possible  that  the  low  differentia- 
tion between  soma  and  germ  may  introduce  experimental 
difficulties  yet  to  be  overcome. 

In  higher  plants  the  observations  of  Zedebauer  with 
Capsella  are  of  interest,  and  introduce  observations  which 


2O4  Heredity  and  Eugenics 

might  be  duplicated  and  extended  by  proper  experimentation 
with  other  plants  and  lead  to  new  and  important  informa- 
tion. A  biotype  of  Capsella,  bursa-pastoris,  much  like 
taraxicafolium,  lives  on  the  low  plains  along  the  coasts  of 
Asia  Minor.  It  has  broad  leaves,  white  flowers,  and  grows 
to  30-40  cm.  high.  On  the  inland  plateau  at  altitudes  of 
2,000-2,500  meters  grows  another  form  with  a  stem  2-5  cm. 
high,  reddish  flowers,  xerophilous  leaves,  and  an  elongated 
root  system. 

From  the  lowlands  roads  lead  to  the  plateau,  and  the 
conditions  of  distribution  are  such  as  to  suggest  that  man 
has  been  influential  in  disseminating  this  form  from  the 
lowlands  to  the  highlands,  where  it  has  taken  on  the  modi- 
fied form.  Some  force  to  this  interpretation  of  the  dis- 
tribution is  given  by  the  fact  that  seeds  from  the  plains, 
when  taken  to  the  plateau,  at  once  assume  the  somatic 
characters  of  the  plateau  type.  On  the  other  hand,  plateau 
seeds,  planted  and  grown  at  Vienna,  while  they  have  the 
xerophilous  character  of  the  leaves,  retain  the  upland  char- 
acters in  flowers,  and,  to  a  large  extent,  in  height,  root 
system,  and  general  habit.  It  is  futile  to  attempt  to  draw 
from  observations  in  nature  such  as  this  conclusions  as  to 
the  past  history  or  actual  happenings,  but  such  instances 
clearly  indicate  the  sort  of  experimentation  that  might 
profitably  be  attempted  and  the  type  of  results  that  might 
be  expected. 

Much  more  concrete  and  accurate  are  the  findings  of 
Klebs  upon  Sempervivum,  in  which  inflorescences  were 
found  to  be  capable  of  replacement  by  a  single  flower,  and 
many  other  changes  were  induced  as  the  result  of  external, 
mainly  climatic,  forces.  More  important  than  the  fact 
of  the  departure  is  the  fact  that  some  changes  persisted 


Modification  of  Germinal  Constitution  of  Organisms       205 

through  three  or  four  generations  in  properly  guarded 
cultures. 

MacDougal  has  attacked  this  problem  from  a  strictly 
experimental  standpoint  in  the  effort  to  discover  a  cause, 
and  to  arrive  at  an  understanding,  of  the  phenomena  of 
"mutation"  as  described  by  DeVries  in  Oenothera.  The 
method  which  he  has  used  is  to  inject  solutions  of  various 
kinds  into  the  ovaries  immediately  before  fertilization. 
Later,  Gager,  by  subjecting  seeds  to  the  action  of  radium 
bromide,  has  shown  that  in  plants  physical  factors  incident 
upon  the  germinal  materials  can  and  do  produce  germinal 
changes  that  are  permanent  and  persist  in  undiminished 
vigor  in  subsequent  generations. 

MacDougal's  experiments,  wherein  zinc  salts,  cane 
sugar,  etc.,  were  injected  into  the  ovules  of  plants,  show 
that  permanent  changes  resulted.  MacDougal's  method 
and  the  reasons  therefor  are  as  follows : 

Having  carried  on  pedigree  cultures  with  a  large  numbe-  of  species 
for  several  years  and  having  encountered  some  which  did  and  others 
which  did  not  give  rise  to  aberrant  individuals,  attention  was  directed 
to  the  possibility  of  inducing  changes  in  the  hereditary  elements  in 
such  a  manner  that  the  qualities  transmitted  would  be  altered  or 
destroyed.  A  theoretical  consideration  of  the  subject  seemed  to 
indicate  that  the  changes  constituting  the  essential  operation  of  muta- 
tion ensued  in  a  stage  previous  to  the  reduction  divisions  in  the  embryo 
sac,  or  the  pollen  mother  cells.  It  was  planned  therefore  to  subject 
these  structures  to  the  action  of  chemical  agents,  not  ordinarily  encoun- 
tered by  the  elements  in  question,  at  a  time  before  fertilization  occurred. 
The  tests  were  planned  to  include  the  use  of  a  solution  of  high  osmotic 
value,  and  mineral  compounds,  some  of  which  are  toxic  in  concentrated 
solutions  and  stimulating  in  the  proportions  used.  The  probability 
of  success  would  be  heightened  with  the  number  of  ovules  contained 
in  any  ovary  operated  upon,  and  therefore  the  common  evening 
primrose,  Oenothera  biennis,  Raimannia  odorata,  a  relative  of  it,  and  a 


206  Heredity  and  Eugenics 

member  of  the  same  family,  Begonia,  Cleome,  Abutilon,  Sphaeralcea, 
and  Mentzelia,  and  others  were  experimented  upon.  Without  recourse 
to  the  detail  of  the  work  it  may  be  stated  that  the  use  of  radium  prepara- 
tions, sugar  solutions  (10  per  cent),  and  solutions  of  calcium  nitrate, 
of  distilled  water,  with  capsules  of  Raimannia  odorata,  and  zinc  sulphate 
in  a  stronger  solution  used  with  Oenothera  biennis  (Fig.  71  A)  was  fol- 
lowed by  very  striking  results.  In  the  first-named  plant,  there  appeared 
in  the  progeny  obtained  from  a  few  capsules  of  one  individual  several 
individuals  which  were  seen  to  differ  notably  from  the  type  with  the 
appearance  of  the  cotyledons,  and,  as  development  proceeded,  it  was 
evident  that  a  mutant  had  appeared  following  the  injections  and 
nowhere  else,  which  thus  had  some  direct  relation  to  the  operation. 
The  characters  of  the  newly  arisen  form  were  so  strikingly  aberrant 
as  to  need  no  skill  in  detection  (Fig.  71.8).  The  parent  was  villous- 
hairy,  the  mutant  entirely  and  absolutely  glabrous,  the  leaves  of  the 
parent  have  an  excessive  linear  growth  of  the  marginal  portions  of  the 
leaf  blades  and  hence  become  fluted;  the  excess  of  growth  in  the  mutant 
lies  along  the  midrib  and  the  margins  become  revolute.  The  leaves 
are  widely  different  in  width,  those  of  the  mutant  being  much  narrower. 
The  parental  type  is  of  a  marked  biennial  habit  and  near  the  close  of 
the  season  the  internodes  formed  are  extremely  short,  which  has  the 
result  of  forming  a  dense  rosette;  the  mutant  forms  no  rosette  by 
reason  of  the  fact  that  the  stem  does  not  cease,  or  diminish  its  rate  of 
elongation  and  hence  presents  an  elongated  leafy  stem,  which  con- 
tinues to  enlarge  as  if  perennial.  The  first  generation  of  the  derivative 
came  to  bloom ;  the  flowers  of  the  mutant  were  closely  guarded  and  as 
soon  as  seeds  were  obtained  they  were  planted  to  obtain  a  second 
generation.  A  few  plants  were  obtained,  which  in  every  particular 
conformed  to  the  new  type  and  exhibited  no  return  to  the  parental 
type. 

MacDougal's  investigations,  wherein  were  produced 
modifications  that  have  remained  stable  through  four  or 
more  generations,  in  Raimannia,  Cereus,  Penstemon,  and 
others,  show  fully  that  the  method  employed  gives  definite 
changes  in  germinal  constitution. 


Modification  of  Germinal  Constitution  of  Organisms      207 


6 

FIG.  71. — Two  plants  of  Onagra  biennis,  showing  the  effect  of  injections  of 
zinc  sulphate  into  the  ovule.  A,  normal.  B,  the  modified  plant,  which  arose 
from  seeds  that  had  been  modified  by  the  zinc  sulphate.  (From  MacDougal.) 


2o8  Heredity  and  Eugenics 

In  Gager's  experiments  the  action  of  radium  rays  and 
emanations  upon  plants  are  definite,  and  in  some  instances 
permanent  modifications  resulted  (Fig.  72).  In  these 
experiments  modifications  by  physical  and  chemical  agents 
were  produced  which  are  not  necessarily  pathological,  and 
some  of  them  continued  to  breed  true  in  subsequent  genera- 
tions. 

Gager  found  that  the  action  of  radium  rays  upon  pollen 
cells  was  to  produce  distortion  of  the  karyokinetic  figure 
to  the  extent  that  chromosomes  were  left  entirely  out  of 
the  spindle  and  were  lost  to  that  particular  germ  cell. 
What  happens  in  any  particular  variant  whose  modifica- 
tions are  inheritable  has  not  been  determined,  but  the  sug- 
gestion is  at  least  plausible  that  the  radium  emanations  in 
some  way  produce  a  new,  or  bring  about  a  rearrangement 
of  the  physiological  complex  which  exists  in  the  germ  cell. 
Conceivably  it  may  be  due  to  the  displacement  of  an  indi- 
vidual chromosome,  although  this  suggestion  would  need 
verification  before  it  could  be  adopted. 

The  modifications  induced  by  the  injections  of  salts 
in  MacDougaPs  experiments  are  not  easy  to  understand. 
The  cells  of  the  ovule  are  relatively  impervious,  and  there 
is  a  relatively  small  amount  of  dispersion  from  the  seat  of 
the  wound.  The  results  obtained,  however,  are  not  due  to 
the  effects  of  wounding,  as  shown  by  the  fact  that  ovules 
wounded  in  the  same  manner  do  not  produce  modifications 
unless  the  salts  are  present;  likewise,  ovules  stung  by  insects 
do  not,  as  far  as  known,  produce  these  results,  and  it  is 
only  in  ovules  into  which  chemical  salts  have  been  injected 
that  modifications  are  effected.  The  conclusion  seems  un- 
avoidable that  the  salts  injected  produced  the  observed 
results  by  modifying  in  some  way  the  constitution  of  the 


FIG.  72. — Showing  effects  of 
rays  of  radium  upon  plants. 
(From  Gager.)  The  plants  in 
this  case  are  Onagra  biennis, 
showing  arrested  development. 
The  ovary  was  exposed  to 
radiations  of  radium  bromide 
(io,oooX)  in  a  sealed  glass 
tube  for  53  hours. 


2io  Heredity  and  Eugenics 

germinal  substance.  MacDougal's  general  conclusion,  as 
to  the  manner  of  producing  this  result,  is  that  the  action  of 
the  injected  chemicals  is  to  accelerate  or  retard  processes, 
especially  those  of  a  katalytic  nature  within  the  germ  cells, 
or  possibly,  actual  chemical  changes  in  germinal  substance 
may  be  affected. 

IN  ANIMALS 

In  animals  the  most  satisfactory  results  have  been 
obtained  with  higher  types,  while  among  the  lower  types, 
Protozoa,  for  example,  changes  by  incident  forces,  though 
capable  of  production,  behave  in  much  the  same  manner 
as  do  changes  induced  in  bacteria  and  yeasts.  In  some 
instances,  variations  persist  for  many  successive  fissions,  but 
they  usually  occur  in  only  one  of  the  individuals  of  each  pair, 
as  in  Jennings'  Paramoecium  with  a  spine.  In  these  in- 
stances there  is  little  or  no  spread  of  the  change  in  the  popu- 
lation through  reproduction  and  thus  far  no  long-continued 
strains  have  been  developed  through  these  agencies.  The 
condition  of  protozoans  in  the  non-differentiation  of  soma 
and  germ,  as  in  bacteria,  is  a  complication  not  easily  over- 
come in  experiment,  and  it  may  well  be,  as  has  been  often 
suggested,  that  the  entire  organism  is  the  "germ  plasm." 

Attempts  to  produce  germinal  changes  by  the  direct 
action  upon  the  germ  of  external  agents  have  not  been  made 
by  many  workers.  Many,  it  is  true,  have  subjected  organ- 
isms to  changed  conditions  and  obtained  modifications, 
aberrations,  but  relatively  few  tests  have  been  made  to 
determine  the  inheritability  of  these  changes. 

The  recent  experiments  of  Woltereck  with  Daphnia 
and  Sumner  with  mice  are  good  examples  of  a  common 
type  of  investigation,  Woltereck  carried  strains  of  Daphnia 
in  cultures  in  which  over-feeding  was  practiced  for  about 


Modification  of  Germinal  Constitution  of  Organisms       21.1 

two  years.  At  the  end  of  this  period  it  was  found  that  the 
head  form  had  changed  and  that  when  the  modified  form 
was  put  back  into  the  original  conditions  the  changed  form 
was  retained.  Unquestionably,  in  Woltereck's  cultures  a 
head  form,  different  from  the  one  with  which  the  culture 
started,  was  present  at  the  end  of  two  years,  and  this  did 
not  revert  on  return  to  normal  conditions;  but  the  failure 
to  carry  adequately  controlled  parallel  normal  lines  does 
not  permit  a  decision  as  to  whether  the  change  is  a  real  one, 
or  due  to  the  progressive  selection  of  a  biotype  present 
but  obscured  in  the  original  population.  Nor  do  the 
experiments  permit  of  a  decision  as  to  whether  the  effects 
observed  were  due  to  direct  germinal  modifications  or  to  so- 
matic transmission.  It  is  shown  that  a  permanent  change 
of  the  race  resulted,  and  nothing  more.  Parallel  cultures 
and  much  more  careful  experimentation  would  be  necessary 
in  the  effort  to  answer  the  more  important  points. 

Similar  in  method  and  in  results  are  the  experiments  and 
conclusions  obtained  by  Kammerer  on  certain  amphibians 
and  Lacertilia.  •  For  example,  Salamandra  maculosa  is 
ovaviparous  in  the  lowlands,  but  its  highland  variety, 
S.  atra,  is  viviparous,  and  the  larvae  are  large  when  born 
and  have  long  gills.  It  was  found  that  lowland  forms  of 
S.  maculosa  kept  without  water  at  low  temperatures  showed 
reproductive  habits  and  young  much  like  those  in  S.  atra 
in  the  alpine  regions.  In  the  lizards,  temperature  was 
found  to  be  productive  of  color  changes,  giving  dimorphism 
in  the  males  of  one  species  and  in  the  females  of  another. 
These  changes  are  alternative  in  crosses. 

In  both  experiments  the  results  have  not  been  carried 
far  enough  to  test  the  inheritance  thoroughly,  and  moreover, 
the  conditions  of  experiment  do  not  permit  of  any  analysis 


212  Heredity  and  Eugenics 

of  the  process  at  the  bottom  of  the  observed  changes.  In 
both,  there  are  changes  following  altered  conditions,  and 
there  have  resulted  changes  in  the  organism  which  are 
known  to  occur  in  many  instances,  only  in  these  experi- 
ments some  effort  was  made  to  test  the  permanency  of 
the  variation  and  its  behavior  in  subsequent  crosses.  In 
both,  the  change  seems  to  be  a  germinal  one,  as  is  indicated 
by  its  behavior  in  inheritance.  Whether  the  change  is  a  di- 
rect germinal  or  an  indirect  one,  due  to  somatic  influence  or 
transmission,  the  experiments  cannot  decide. 

Precisely  similar  are  Sumner's  experiments  in  sub- 
jecting mice  to  high  and  low  temperatures,  where  at  the 
end  differences  were  found  which  were  attributed  to  the 
effect  of  the  different  conditions.  Differences  there  were 
at  the  end,  but  in  mammals  so  variable  as  mice  carefully 
pedigreed  strains  free  from  bio  types  should  have  been  used, 
and  adequate  parallel  controls  should  have  been  main- 
tained. In  that  controls  of  critical  character  were  lack- 
ing and  the  possibility  of  biotypes  was  not  eliminated  from 
the  stock  used,  the  results  obtained  are  easily  attributed  to 
gradual  selection  of  biotypes  or  of  actuation  of  latent 
characters,  as  well  as  to  the  effect  of  changed  temperatures. 
As  for  the  question  of  somatic  influence  or  direct  germinal 
effect,  the  experiments  are  not  conducted  so  as  to  give  proper 
evidence  thereon  and  are  capable  of  any  interpretation. 
The  experiments  show,  however,  that  changed  conditions 
changed  the  stock,  which  change  may  have  resulted  from 
any  of  the  methods  suggested,  and  the  change  is  appar- 
ently permanent  although  the  series  was  too  short  to  answer 
this  question  adequately. 

In  insects,  I  have  obtained  modifications  in  various 
ways,  some  of  which  will  be  described  in  a  later  portion 


Modification  of  Germinal  Constitution  of  Organisms       213 

of  the  chapter.  Morgan,  in  Drosophila  ampelophila  Low, 
found  that  sex-limited  variations  of  pink  eye,  etc.,  have 
apparently  followed  the  treatment  of  cultures  of  this  animal 
to  the  action  of  radium  bromide.  Loeb,  however,  using  the 
same  organism,  found  that  in  both  experiment  and  control 
the  variation  described  by  Morgan  appeared,  and  of  course 
concluded  that  the  tendency  to  produce  this  variation  was 
already  present  in  the  race  of  flies  used. 

Lutz  had  for  several  years  used  the  same  strain  of 
Drosophila  for  experiment,  and  found  much  variation  in  wing 
venation.  He  also  subjected  the  strain  at  times  to  different 
experimental  conditions,  and  this  may  be  responsible  for  the 
appearance  of  the  variation  found  by  Morgan  following  the 
use  of  radium,  and  which  appeared  in  experiment  and  control 
in  Loeb's  experiments. 

In  Chrysomelid  Beetles 

In  the  modification  of  the  germinal  constitution  by 
experimental  means  it  must  be  known  as  certainly  as  is 
possible  whether  there  are  in  the  germ  potential  capacities, 
i.e.,  latent  characters,  which  ordinarily  are  not  visible  in 
the  materials  used,  but  which  may  be  called  into  visibility, 
periodically  or  rarely,  by  unusual  conditions.  Unless  pos- 
sibilities of  this  kind  are  eliminated,  it  becomes  difficult 
in  experiment  to  decide  whether  observed  results  are  the 
product  of  latent  conditions,  or  of  the  experiment  as  de  novo 
variations.  Moreover,  experiments  to  show  the  effect 
of  incident  conditions  upon  the  germinal  material  must, 
beyond  any  question,  show  that  the  effect  is  primarily 
upon  the  germ  and  not  first  upon  the  soma  of  the  parent, 
and  secondarily,  by  transmission,  to  the  germ.  If,  in 
experiment,  the  soma  of  the  parent  and  of  the  resulting 


214  Heredity  and  Eugenics 

progeny  be  modified  in  the  same  manner,  there  are  two 
possible  explanations.  The  incident  conditions  may  modify 
both  soma  and  germ  independently,  and  they  would  be 
similarly  modified  because  both  soma  and  germ  represent 
one  and  the  same  group  of  potentialities;  or  the  observed 
results  can  be  explained  by  assuming  that  incident  conditions 
first  modify  the  soma,  and  secondarily,  through  transmission, 
the  modification  is  incorporated  into  the  germ  cell;  and 
thus  be  interpreted  as  upholding  the  neo-Lamarckian  idea 
of  the  inheritance  of  acquired  soma  variations.  It  follows, 
therefore,  that  the  germ  cells  upon  which  experiments  are  to 
be  carried  out  must  either  be  taken  from  the  body  of  the 
parent  and  placed  in  indifferent  media  before  being  experi- 
mented upon,  or  they  must  be  in  organisms  that  can  under- 
go no  further  somatic  modifications.  In  this  there  could, 
of  course,  be  no  transmission  of  acquired  variations,  because 
no  variations  are  acquired.  Moreover,  for  our  purpose 
any  resulting  change  must  be  thoroughly  tested  by  subse- 
quent breeding  for  many  generations. 

When  these  organisms  attain  sexual  maturity,  they  have 
attained  all  of  the  somatic  modifications,  save  pathological 
growths,  which  it  is  possible  for  them  to  achieve;  the  onto- 
genetic  development  of  variations  has  come  to  a  standstill, 
the  whole  activity  of  the  organism  is  directed  to  reproducing 
the  species,  and  further  development  or  divergence  in  any 
of  its  attributes  or  qualities  is  forever  inhibited.  Whatever 
changes  occur,  from  sexual  maturity  onward,  are  pathological 
or  senescent. 

It  is  possible,  therefore,  to  eliminate  from  these  experi- 
ments the  neo-Lamarckian  factor,  because  the  conditions 
of  experiment  were  not  applied  until  after  the  parents  had 


Modification  of  Germinal  Constitution  of  Organisms       215 

attained  full  sexual  maturity  and  complete  development 
of  all  qualities  and  attributes. 

A  check  upon  the  possible  latent  characters  is  more 
difficult,  but  in  this  material  it  is  easily  carried  out  in  one 
of  two  ways:  First,  only  pedigreed  material  was  used  in 
experiment.  This  material  has  always  been  tested  by  cross- 
ing within  and  without  the  species  to  discover,  as  far  as 
possible,  any  characters  which  might  be  present  in  invisible 
conditions.  Thus  far,  no  attributes  of  this  description  have 
been  discovered.  Second,  a  check  was  kept  upon  this 
possible  source  of  error  in  the  following  way:  these  beetles 
have  the  habit  of  maturing  their  eggs  in  definite  rotation; 
that  is,  a  batch  of  eggs  is  developed,  fertilized,  and  laid; 
then  a  time  interval  elapses  during  which  another  batch  of 
eggs  is  being  developed,  and  this  is  repeated  many  times, 
thus  giving  isolated  lots  of  eggs,  each  separated  from  the 
one  before  by  a  time  interval  of  from  two  to  sixty  days, 
or  even  more,  and  any  one  of  which  may  be  subjected  to 
experiment  and  the  others  used  as  controls.  In  many  of 
these  experiments  color  has  served  as  a  useful  character  for 
study  and  the  results  from  the  experimental  modification 
of  color  may  be  presented  first. 

Experimental  modification  of  color. — Color  modifications 
are  of  two  distinct  kinds:  changes  in  the  pigment  itself, 
and  in  the  localization  thereof.  The  first  is  a  chemical 
change  produced  by  a  rearrangement  of  the  chemical 
activities  existing  between  a  chromogen  and  an  enzyme 
which  brings  the  color-forming  compounds  into  existence, 
while  the  latter  is  a  change  in  the  localization. 

Variations  in  color  usually  are  either  accentuations  or 
diminutions  of  existing  color,  and  these  changes  are  perma- 


2l6 


Heredity  and  Eugenics 


nent,  are  not  pathological,  and  the  individuals  possessing 
them  are  by  no  means  weaklings,  which  has  been  shown  in 
the  case  of  L.  pallida  (Fig.  73^),  which  was  produced  in 
considerable  numbers  as  a  variation  of  L.  decemlineata  Say, 


D  C 

FIG.  73. — Some  divergent  types  of  beetles  produced  by  subjecting  the  germ 
cells  to  external  influences.  A,  normal  decemlineata.  B,  the  form  pallida.  C, 
tortuosa.  D,  defecto-punctata. 

in  some  of  my  earlier  cultures.  This  modification  represents 
definitely  a  decrease  in  the  pigmentation  values  of  the  organ- 
ism, with  slight  changes  in  bodily  proportions,  punctation, 
habits,  etc.  It  arises  by  subjecting  the  organism  to  rigor- 


Modification  of  Germinal  Constitution  of  Organisms       217 

ous  conditions,  especially  high  temperature  accompanied 
by  low  relative  humidity.  Such  variants  have  been  found 
in  nature,  some  of  them  are  known  to  breed  true,  and 
others  are  produced  in  experiment. 

Fig.  74  shows  a  photograph  of  a  demonstration  case 
exhibiting  the  results  from  an  experiment  of  this  kind. 
Here  the  parent  pair  are  shown  producing  the  two  first  lots 
of  eggs  which  developed  into  normal  individuals  which 
were  in  following  generations  true  to  type,  while  the  third, 
fourth,  and  fifth  lots  of  eggs  were  experimented  upon  and 
gave  in  each  modified  types,  pallida  and  minuta,  as  well  as 
some  normals.  These  different  types,  when  inbred,  came 
true  to  type  in  subsequent  generations,  as  shown. 

Another  divergent  type  which  arose  in  the  same  series 
of  experiments  is  one  in  which  the  pigmentation  is  increased, 
that  is,  the  amount  of  dark  pigment  in  the  color  pattern 
gave  the  resulting  individual  a  different  appearance  from  that 
of  the  parent  species.  Both  pallida  and  melanicum  (Fig. 
73^4)  were  true  breeding  germinal  variations,  and  pallida 
when  given  a  fair  start  showed  itself,  at  least  in  certain 
cultures,  to  be  capable  of  sustaining  itself  in  competition  with 
the  parent  species ;  mclanicum,  however,  did  not  exhibit  any 
such  potentiality. 

If  a  form  like  L.  pallida  were  to  develop  in  an  arid  area 
it  would  be  recognized,  as  I  have  suggested,  as  a  step  in  the 
process  of  evolution,  and  it  would  be  directly  attributed,  if 
it  were  found  in  nature,  to  the  conditions  under  which  it 
was  living,  and  its  existence  would  be  explained  either  by 
natural  selection,  or  some  other  of  the  current  hypotheses. 

Other  modifications  which  have  arisen  from  L.  decem- 
lineata,  especially  in  the  modification  of  the  hypodermal 
lipoid  pigments,  are  distinctly  not  the  increase  or  decrease 


FIG.  74. — Photograph  of  demonstration  case  which  has  been  arranged  to 
show  the  effects  produced  upon  the  progeny  of  a  single  pair  of  beetles  by  subjecting 
the  ova  to  strong  incident  physical  forces,  before  and  during  fertilization.  To  the 
left  is  represented  the  normal  stock,  showing  no  presence  during  the  time  of  experi- 
ment of  the  modified  forms.  The  first  two  lots,  A  and  B,  were  laid  and  matured 
under  normal  conditions  and  gave  normal  types.  Lot  C,  laid  and  matured  under 
the  conditions  of  the  experiment,  gave  part  modified  and  part  unmodified  forms. 
The  same  is  true  of  Lots  D  and  E.  The  modified  types  in  this  experiment  were 
mainly  pallida,  clearly  distinguishable  in  the  photograph  by  their  lighter  and 
smaller  form;  they  breed  true  in  successive  generations  as  indicated  in  the 
demonstration  case. 


22o  Heredity  and  Eugenics 

in  the  amount  of  pigmentation,  but  represent  the  rapid 
changes  which  are  characteristic  of  lipochrome  pigments: 
for  example,  in  rubrivittata,  in  which  the  most  striking 
character  is  the  bright  red  hypodermal  color.  This  arises 
suddenly  as  the  result  of  experimental  conditions  and 
reproduces  itself  when  bred  back  to  the  parent  species, 
giving  a  color  segregation  into  rubrivittata  and  hybrids,  the 
rubrivittata  breeding  true.  The  behavior  of  rubrivittata 
is  such  as  to  suggest  that  in  its  main  distinctive  character 
it  is  recessive  to  the  parent  species. 

In  modifications  of  color  we  are  dealing  with  superficial 
chemical  processes  in  the  organism — the  development  of  a 
chromogen  and  the  oxidation  of  that  chromogen  by  one  or 
more  oxidizing  enzymes  to  a  state  of  stability  where  simpler 
compounds  are  produced  which  are  productive  of  color. 
In  no  experiments  in  the  modification  of  color,  especially 
in  colors  such  as  the  melanins,  etc.,  has  any  modification 
been  produced  which  is  not  an  accentuation  or  diminution 
of  the  oxidative  capacity  of  the  organism.  That  is,  in 
the  case  of  pallida,  there  is  a  decrease  in  the  capacity  of  the 
organism  to  produce  either  (i)  the  necessary  oxidizing 
agents,  or  (2)  the  requisite  amount  of  chromogen,  or  (3) 
the  capacity  of  the  organism  to  sustain  the  conditions 
necessary  for  the  oxidative  processes  a  sufficiently  long 
time  to  enable  a  given  amount  of  chromogen  to  be  oxidized 
to  produce  a  stated  amount  of  pigment. 

It  has  long  been  known  that  the  series  of  color  changes 
may  proceed  from  white,  through  yellowish,  yellowish- 
brown,  reddish-brown,  deeper  browns,  and  finally  to  black, 
then  to  a  still  further  stage  of  oxidation — white,  so  that 
with  a  given  amount  of  chromogen  and  a  given  amount  of 
oxidizing  enzyme,  diverse  results  can  be  obtained  from 


Modification  of  Germinal  Constitution  of  Organisms       221 

identical  materials,  simply  by  the  duration  of  time  which 
the  process  is  allowed  to  act.  This  can  readily  be  shown 
in  any  of  this  material  in  the  ontogenetic  development  of 
the  individual.  The  oxidative  process  may  be  stopped  at 
any  stage,  and  the  coloration  of  the  organism  then  remains 
at  the  stage  in  which  the  oxidation  was  stopped.  On  the 
other  hand,  the  process  may  be  continued  for  an  abnor- 
mally long  time,  producing  an  unusual  amount  of  pigment 
substances,  giving  the  organism  a  dark  appearance. 

We  are  ignorant  of  any  mechanism  in  the  germ  cell 
which  would  bring  about  such  inhibition  of  the  oxidative 
process,  supposing  that  the  amount  of  chromogen  and 
oxidizer  remains  the  same.  Of  course  one  could,  in  explain- 
ing this  condition,  adopt  the  idea  developed  by  Davenport 
of  the  existence  of  inhibitors,  and  while  it  is  highly  probable 
that  there  are  such  inhibitors  present  in  the  germinal 
mechanism,  information  concerning  them  is  so  fragmentary 
that  any  extended  use  thereof  in  explaining  these  phenomena 
would  better  be  postponed. 

The  interpretation  of  the  results  produced  is  that  the 
germinal  complex  has  been  permanently  modified  in  some 
way,  such  that  either  the  chromogen  is  not  present  in 
sufficient  amount  to  produce  the  color  of  the  parental  genera- 
tion, or  the  oxidation  is  deficient,  but  which  of  the  two 
possibilities  is  correct  cannot  at  the  present  time  be  decided. 
It  is  entirely  probable  that  it  might  be  one  in  some  instances 
and  in  another  the  other  factor  that  was  deficient,  both 
conditions  bringing  about  identical  results.  It  does  not 
follow  from  this  that  there  exists  in  the  germ  a  definite 
representative  of  the  chromogen  and  of  the  katalytic  agent. 

In  the  germ  cells,  as  in  all  other  cells,  oxidases  and  sub- 
stances which  may  serve  as  a  chromogen  are  present  and 


222  Heredity  and  Eugenics 

this  capacity,  therefore,  for  the  production  of  pigmentation 
is  not  something  which  is  conditioned  by  any  particular 
thing  in  the  cell,  but  it  represents  a  capacity  common  to  all 
living  substances. 

In  what  way  is  the  constitution  of  the  germ  cell 
modified  so  that  the  organism  shows  in  subsequent  gen- 
erations a  permanent  change  in  its  coloration  ?  It  has 
been  pointed  out  to  me  by  Professor  Morgan  that  in  these 
experiments  the  behavior  in  the  first  generation  is  difficult 
of  interpretation.  In  these  experiments  the  male  cells 
or  the  female  cells,  and  sometimes  both,  have  been  sub- 
jected to  conditions  of  experiment  at  a  susceptible  stage. 
Eggs  are  most  susceptible  immediately  before  and  during 
maturation,  although  what  connection  this  has  to  the 
maturation  process  is  not  known. 

Morgan  has  raised  the  question,  why  do  individuals,  de- 
veloped from  eggs  which  have  been  subjected  to  conditions  of 
experiment  and  fertilized  with  normal  sperm,  not  give  a  sub- 
sequent hybrid  behavior  ?  No  hybrid  splitting  has  ever  been 
found  in  any  of  my  experiments,  or  in  those  of  MacDougal 
or  Gager.  The  resulting  modification  reproduces  itself  true 
to  type,  and  does  not  give  subsequent  splittings  suggestive 
of  the  combination  of  different  factors  or  unit-characters. 
If  there  are  unit-characters,  it  is  logical  to  expect  that  in 
experiments  of  this  kind  the  experiment  would  modify 
the  unit-character  in  the  germ  plasm,  and  that  this  modified 
unit-character  would  then  behave,  when  crossed  with  its 
normal  homologue,  exactly  as  hybrids  do  in  other  cultures. 
The  total  lack  of  this  behavior  in  my  experiments,  and  those 
of  MacDougal,  Gager,  and  others,  might  be  considered 
good  evidence  that  there  are  no  such  things  as  unit- 
characters,  nor  in  the  germ  cells  any  potentiality  capable 


Modification  of  Germinal  Constitution  of  Organisms       223 

of  individual  removal  or  behavior.  Any  such  deduction, 
however,  is  unwarranted  and  contrary  to  known  facts,  and, 
furthermore,  these  modified  characters  themselves  show  that 
after  establishment  they  are  alternative  and  capable  in  many 
instances  of  replacement  and  recombination  in  full  conform- 
ity with  established  principles  of  heredity  behavior. 

How  shall  this  behavior,  which  has  been  observed  by 
MacDougal,  Gager,  myself,  and  others,  in  the  production 
of  these  variations,  be  interpreted?  MacDougal's  inter- 
pretation, in  the  case  of  plants,  is  that  the  modifications 
induced  are  due  to  the  modifiability  of  the  enzyme  action 
in  one  way  or  another.  Gager  attributes  the  activity  to 
the  derangement  of  the  chromosomes  by  the  radium  emana- 
tions. In  beetles,  I  do  not  know  that  the  chromosomes 
are  deranged  by  any  of  the  processes,  and  we  do  not  know 
that  the  chromosomes  are  the  specific  bearers  of  any  par- 
ticular attributes.  The  explanation  which  appeals  most 
strongly  to  me  in  the  case  of  eggs  which  have  been  subjected 
to  strong  incident  forces  is  that  the  change  should  be 
regarded  as  an  example  of  stereoisomeric  change,  whether  in 
the  composition  of  the  katalyzing  agent,  or  in  the  composi- 
tion of  the  chromogen,  or  in  some  accelerator  or  inhibiting 
agent  in  the  germ  plasm.  It  is  quite  conceivable  that  the 
change  may  take  place  in  the  chromogen.  As  far  as  known, 
all  chromogens  are  substances  of  wide  distribution  in  all 
organisms  with  slightly  different  chemical  characteristics, 
and  it  is  highly  probably  that  there  is  a  wide  range  of 
chemical  composition  in  these  chromogens,  so  that  a  slight 
change  in  the  arrangement  of  the  molecular  composition 
of  the  chromogen  could  be  productive  of  the  results  observed. 
At  present,  however,  there  is  little  possibility  of  obtaining 
definite  evidence  along  this  line,  because  the  present  methods 


224  Heredity  and  Eugenics 

of  physiological  chemistry  are  so  exceedingly  gross  that 
when  by  any  available  method  either  chromogen  or  enzyme 
have  been  removed,  they  have  been  changed  to  a  very 
considerable  degree  in  structure  and  relations,  and  possibly 
in  capacity  for  pigment  production.  The  complexity  and 
almost  futile  nature  of  the  chemical  side  of  this  problem  is 
clearly  indicated  by  the  statement  (Meischer)  that  in 
albumen  molecules  containing  no  more  than  forty  carbon 
atoms  there  are  something  like  a  billion  possible  stereo- 
isomeres.  It  is  at  once  evident  how  utterly  hopeless  it  is 
with  present  methods  to  expect  exact  chemical  determina- 
tions of  these  germinal  changes,  and  the  best  that  the 
physiological  chemist  can  be  expected  to  do  is  to  show  the 
grosser  outlines  of  the  possible  processes  involved.  To 
determine  the  exact  changes  within  the  germ  cell  is  at 
present  not  possible. 

Furthermore,  the  results  of  Reichert  and  Brown  upon 
the  investigation  of  haemoglobin  crystals  have  shown  a  great 
array  of  crystalline  forms  and  structures  in  this  substance 
in  allied  mammalia,  and  it  is  highly  probable  that  other  sub- 
stances throughout  the  organic  world  are  equally  divergent, 
equally  complex,  and  equally  specific.  We  must  therefore 
keep  in  mind  that  in  these  color  modifications  there  are 
always  three  possibilities — the  modification  of  the  chromo- 
gen base,  the  modification  of  the  enzyme,  or  the  modification 
of  the  capacity  for  carrying  on  the  process;  but  present  evi- 
dence, I  believe,  warrants  a  stronger  belief  in  the  efficiency 
of  modifications  in  the  capacity  of  carrying  on  the  process 
more  than  in  the  modification  of  either  the  chromogen  base 
or  the  katalyzer,  i.e.,  to  modified  accelerators  and  inhibitors. 

In  colors  due  to  lipoids,  modifications  thereof  might  be 
attributable  to  changes  in  the  chromogen  base,  in  the 


Modification  of  Germinal  Constitution  of  Organisms      225 

katalyzer,  or,  in  some  cases,  perhaps,  to  the  stereoisomeric 
relations  in  the  molecules  which  are  attached  to  the  fatty 
base.  The  well-known  changes  which  are  possible  in  the 
case  of  lipochrome  colors,  changing  with  sharp  alternative- 
ness  from  red  to  yellow,  from  orange  to  white,  or  vice 
versa,  are  quite  possibly  due  to  reversibility  in  some  enzyme 
within  the  germ  cell,  and  this  reversed  action  remains 
reversed  until  such  time  as  it  is  again  changed  in  its  direction 
by  incident  factors.  That  this  is  apparently  the  correct 
explanation  of  the  behavior  of  this  particular  type  of 
pigmentation  activity  seems  to  be  fully  shown  by  many 
experiments. 

In  many  of  my  experiments  germ  cells  that  were  pro- 
duced at  a  time  when  the  lipochrome  pigment  in  the  parents 
was  yellow,  produced  yellow  progeny,  but  when  the  color 
had  been  experimentally  reversed  they  gave  white,  orange, 
or  red  progeny,  depending  upon  the  direction  of  change  in 
the  parent.  These  results  strongly  indicate  that  the  inter- 
pretation which  I  have  placed  upon  this  type  of  germinal 
variation  is  the  correct  one. 

Variations  in  these  lipoid  color  characters  are  common  in 
plants  and  animals,  and  characters  based  upon  these  are 
widely  used  as  specific  differentials,  and  they  are  permanent 
so  long  as  a  given  state  of  equilibrium  exists.  This  state 
of  equilibrium,  however,  can  be  reversed  or  upset,  producing 
reversed  conditions,  and  these  reversed  conditions  can  again, 
after  an  indefinite  period,  be  brought  back  to  the  first 
condition,  or  some  other  condition,  by  incident  forces.  It  is 
almost  heresy  at  the  present  time  to  suggest  the  possibility 
of  reversibility  in  evolutionary  action,  but  the  reversible 
nature  of  many  characters  of  importance  in  evolution  is  by 
no  means  unthinkable  and  is  susceptible  of  experimental 


226  Heredity  and  Eugenics 

investigation.  The  dogma  of  the  irreversibility  of  evolution 
processes,  which  has  grown  out  of  phylogenetic  and  onto- 
genetic  study,  is  incompatible  with  a  physico-chemical  in- 
terpretation of  nature,  and  has  no  basis  at  present  in  critical 
experimental  investigation. 

These  germinal  modifications  of  color  characters  indicate 
an  approach  to  an  understanding  of  germinal  variations  in 
certain  attributes;  that  is,  it  is  understood  what  might 
happen,  but  in  no  case  is  it  known  what  did  happen,  nor 
how.  These  variations  in  color  concern  superficial  attributes 
in  the  economy  of  the  organism;  and  the  mere  production 
of  a  color-producing  substance  is  to  a  greater  or  less  extent 
only  an  incident  in  the  life  of  the  organism.  Colors  are 
produced  pathologically  or  otherwise  in  these  organisms, 
by  wounding,  by  disease,  etc.,  at  will,  showing  that  there  is 
throughout  the  organism  the  capacity  for  the  production 
of  color  compound  which  lies  at  the  basis  of  the  normal 
coloration.  The  greater  problem  lies  not  in  the  production 
of  color  changes,  but  in  the  processes  which  are  productive 
of  the  localization  of  pigments  into  a  color  pattern,  and  it  is 
this  attribute  of  pattern  which  differentiates  organisms  most 
certainly  from  inorganic  substances.  What  is  it  that  is 
productive  of  pattern,  and  in  which  way  may  the  color  be 
modified  ? 

Experimental  modification  of  pattern. — The  pattern  is  an 
attribute  by  no  means  so  easy  to  modify  as  is  color,  but  it 
has  been  found  that  the  pattern  is  less  modifiable  by  incident 
forces  than  other  parts  of  the  organism.  Of  those  instances 
in  which  the  pattern  has  been  modified,  as  in  albida,  tortuosa, 
minuta,  and  dejecta  punctata  (Fig.  736"),  all  proved  to  be 
germinal  variations  and  to  breed  true,  but  the  difficulty  in 
breeding  many  of  them  and  their  inability  to  exist  under 


Modification  of  Germinal  Constitution  of  Organisms       227 

the  conditions  into  which  they  were  born  lead  one  to 
conclude  that  what  is  actually  produced  in  many  of  these 
modifications  are  pathological  germinal  variations,  rather 
than  healthy  germinal  conditions  which  can  be  perpetuated 
indefinitely  in  nature.  It  should  further  be  noted  that  in 
these  modifications  the  changes  were  essentially  in  the 
amount  of  pigment  which  was  produced  in  definite  areas, 
especially  in  the  color  pattern  of  the  pronotum  and  elytra, 
and  while  the  change  existed  through  the  body  as  a  whole,  it 
is  not  thereby  established  that  the  fundamental  pattern 
upon  which  these  attributes  are  based  was  in  any  way 
altered.  All  that  is  certain  is  that  there  was  produced  a 
permanent  modification  of  the  capacity  to  produce  pigment 
in  the  form  of  spots  or  stripes  in  definite  areas. 

In  these  modified  organisms  the  capacity  to  produce 
pigment  is  by  no  means  absent,  as  for  example,  in  albida, 
where  dark  color  could  be  subsequently  produced  upon  any 
part  of  the  body  by  wounds,  etc.,  giving  a  considerable 
amount  of  the  same  dark  pigment  in  the  hypodermis  and 
in  the  lower  layers  of  the  cuticula.  The  capacity  to 
produce  both  the  oxidizing  agent  and  the  chromogen  is 
present,  but  the  pigment  is  not  produced  in  a  definite  loca- 
tion; in  other  words,  whatever  it  is  in  the  organism  that 
determines  localization  is  inactive,  and  pigment  production 
is  inhibited  by  some  unknown  inhibitor. 

The  production  of  variations  in  pattern  by  means  of 
intense  stimuli  has  not,  in  my  experience,  been  accompanied 
by  what  I  regard  as  conspicuous  success.  Variations  have 
been  produced,  but  these  variations  are  often  of  a  pathologi- 
cal character  and  could  not  be  produced  under  the  condi- 
tions imposed  by  nature.  Permanent  variations,  however, 
in  the  pattern  are  obtainable  by  a  combination  of  external 


228  Heredity  and  Eugenics 

forces  with  selective  accumulation,  provided  the  impact  of 
the  external  forces  is  not  made  too  intense.  In  other  words, 
variations  properly  combined  lead  to  more  definite  results  in 
the  modification  of  pattern  than  the  more  vigorous  methods 
which  are  productive  of  permanent  changes  in  color.  It  is 
therefore  necessary  to  distinguish  between  the  modifications 
of  color  and  modifications  of  color  pattern,  because  pat- 
tern may  well  be  present  as  an  attribute  without  revealing 
itself,  and  it  only  reveals  itself  when  something  in  the 
organism  results  in  the  deposition  of  color  in  the  proper 
location. 

In  the  experimental  modification  of  organisms,  the  pat- 
tern has  been  one  of  the  characters  least  influenced.  In 
DeVries'  experiments  with  plants  the  pattern  was  modified 
relatively  little,  if  at  all,  the  principal  changes  in  Oenothera 
being  in  leaf  proportion,  leaf  arrangement,  color,  and 
similar  characters,  which  are  properties  of  the  whole  and 
which  are  known  to  vary  with  more  or  less  readiness  in  all 
organisms.  In  the  same  way  the  experiments  which  have 
been  carried  out  on  insects  by  Dorfmeister,  Weismann, 
Fischer,  Edwards,  Standfuss,  and  many  others,  show  modi- 
fications in  the  color  and  little  or  no  modification  in  the 
pattern.  In  some  specimens  the  pattern  is  obscured  by  the 
spreading  of  the  color  from  the  original  area  into  contiguous 
portions,  but  the  fundamental  pattern  itself  is  not  altered, 
as  shown  by  the  fact  that  in  most  of  these  experiments  in 
the  next  generation  the  progeny  revert  to  the  pattern  of 
the  normal  parental  stock. 

In  MacDougal's  experiments  with  plants,  and  in  Gager's 
also,  the  pattern  appears  to  be  only  slightly  modified,  if  at 
all,  and  in  all  of  the  plants  used  by  them  the  pattern  was 
relatively  simple,  both  petals  and  leaves  being  self-colored, 


Modification  of  Germinal  Constitution  of  Organisms       229 

and  the  variations  which  occurred  were  mainly  variations 
which  resulted  from  modifications  of  the  growth  processes, 
influencing  leaf  proportions,  and  such  characters  as  pubes- 
cence, color,  etc. 

In  experiments  with  beetles,  I  have  found  that  the 
subjection  of  organisms  to  unusual  environmental  stimuli 
did  not  as  a  rule  materially  change  the  pattern,  and  never, 
as  far  as  I  have  observed,  did  it  in  any  way  alter  the  funda- 
mental pattern  basis  of  the  organism.  It  might  appear 
on  superficial  inspection  that  the  pattern  existed  in  its  origi- 
nal simplicity,  even  if  it  were  not  manifest  to  the  eye.  For 
instance,  in  defecta  punctata,  it  is  the  inability  of  the  pigment, 
through  some  cause  or  other,  to  be  developed  in  particular 
areas.  This  inhibition  of  pigmentation  may  be  due  to  the 
oxidizing  of  the  pigment  to  a  colorless  state.  On  the  other 
hand,  in  variations  like  melanicum,  in  which  the  color  pat- 
tern of  many  of  the  parts  is  distinctly  different,  as  far  as 
superficial  inspection  is  concerned,  the  underlying  pattern 
is  unaltered,  and  that  which  goes  to  make  up  the  difference 
between  melanicum  and  the  parent  species  is  simply  added 
development  and  extension  of  the  color  from  the  original 
areas  around  which  they  develop.  This  is  shown  by  the 
fact  that  during  the  ontogeny  in  melanicum  there  is  an 
exact  recapitulation  of  the  stages  through  which  melanicum 
has  passed  in  reaching  its  present  state.  This  represents 
an  accentuation  of  existing  characters  along  definite  lines. 

In  variations  of  another  kind  there  are  indications  that 
fundamental  changes  in  the  pattern  occur.  L.  melanothorax 
Stal,  bears  a  relation  to  the  species  L.  multitaeniata  Stal 
either  of  a  constantly  recurring  mutant  which  is  unable 
to  survive  the  conditions  under  which  it  arises,  or  may 
represent  the  constant  reappearance  of  a  species  which 


230  Heredity  and  Eugenics 

has  been  absorbed  by  multitaeniata,  but  not  completely 
incorporated — traces  of  it  occurring  in  every  generation 
with  greater  or  less  frequency.  Both  the  melanothorax 
and  multitaeniata  develop  among  the  progeny  of  the  same 
parents,  and  between  them  there  is  a  striking  difference  in 
the  development  of  the  pattern.  Both  start  from  essen- 
tially the  same  base,  but  melanothorax  diverges  with  great 
rapidity  and  does  not  pass  through  the  stages  of  the  parents 
from  which  it  came,  as  shown  in  Fig.  75. 


—v 
•     •       • 


••  ••**** 


FIG.  75. — To  show  the  sequence  of  stages  in  ontogeny  in  L.  multitaeniata  (A) 
and  its  recurrent  mutant,  melanothorax  (B).  It  should  be  noted  that  the  latter 
form  has  its  own  type  of  development  and  diverges  from  the  parental  condition, 
having  very  little  in  common  with  L.  multitaeniata  from  which  it  came.  This 
suggests  that  this  type  of  development  is  as  much  a  specific  and  independent 
character  as  is  its  final  form. 

In  a  pure  strain  of  L.  multitaeniata  Stal,  where  no  traces 
of  melanothorax  were  observed  for  several  generations, 
injections  of  dilute  solutions  of  calcium  nitrate  caused  it 
to  give  melanothorax.  In  these  induced  forms  the  ontogeny 
of  the  color  pattern  is  the  same  as  in  the  development  of 
material  found  in  nature.  This  behavior  of  melanothorax 
represents  another  type  of  pattern  modification — a  rapid 
divergence  from  the  initial  state  common  to  a  very  wide 
range  of  species,  and  in  no  wise  is  it  a  repetition  of  the 


Modification  of  Germinal  Constitution  of  Organisms       231 

ontogenetic  history  of  the  parent  from  which  it  came.  In 
view  of  the  fact  that  the  real  relation  which  exists  between 
L.  multitaeniata  and  L.  melanothorax  must  remain  unknown, 
no  conclusion  as  to  the  significance  of  this  wide  divergence 
in  the  development  of  the  color  pattern  can  be  safely 
drawn.  The  relation  between  L.  multitaeniata  and  L. 
melanothorax  may  be  that  of  two  hybridizing  species  in 
which  L.  melanothorax  is  in  the  process  of  assimilation,  and 
if  this  attribute  is  a  "unit-character"  it  follows  that  in  the 
reappearance  of  the  recessive  form  which  L.  melanothorax 
appears  to  be,  it  is  to  be  expected  that  the  recessive  char- 
acter would  exhibit  the  ontogenetic  series  of  stages  charac- 
teristic of  itself,  and  not  those  of  the  parent  species  out 
of  which  it  came.  There  is,  however,  another  possibility, 
namely,  that  the  reappearance  of  L.  melanothorax  in  each 
generation  of  L.  multitaeniata  may  be  considered  a  recurring 
mutation  which  diverges  in  its  direction  independently  of 
the  parental  type. 

This  observed  condition  can  be  explained  on  the  basis 
of  multifarious  mutations  in  the  sense  of  DeVries,  or  on  the 
basis  of  unit-characters  recessive  to  L.  multitaeniata,  but 
recurring  with  greater  or  less  frequency.  Under  condi- 
tions of  nature  it  is  not  possible  to  determine  which  one  of 
these  two  possibilities  is  the  correct  one. 

2.    HYBRIDIZATION 

The  results  obtained  by  the  horticulturist  and  husband- 
man through  hybridization  in  achieving  the  modifications 
of  plants  and  animals  which  are  desired  have  long  been 
known,  and  in  plants  a  very  considerable  array  of  the  modi- 
fications produced  never  get  beyond  the  first  hybrid  genera- 
tion and  are  perpetuated  by  cuttings,  or  other  forms  of 


232  Heredity  and  Eugenics 

asexual  reproduction.  In  animals  a  considerable  array  of 
domesticated  forms  are  definitely  the  product  of  hybridiza- 
tion. Poultry,  for  example,  are  derived  from  two  or  three 
original  stocks  which  have  been  intercrossed  numberless 
times,  and  from  these  crosses  have  resulted  variations  in 
the  arrangement  of  the  parental  characters  and  combina- 
tions of  characters.  The  same  is  true  of  domesticated 
pigeons,  where  hybridization  has  been  carried  out  to  a  very 
great  extent,  and  in  dogs,  cats,  mice,  rabbits,  rats,  guinea- 
pigs,  swine,  and  in  practically  all  domesticated  organisms 
essentially  the  same  condition  exists.  Unfortunately,  in 
domesticated  organisms  the  beginning  of  these  modi- 
fications is  shrouded  in  antiquity,  and  while  man  has 
reared  dogs,  swine,  pigeons,  and  poultry  for  a  long  period, 
and  while  there  have  arisen  under  his  hand  the  variations 
which  are  now  seen  under  domestication,  the  manner  of 
origin  is  unknown,  and  the  best  that  can  be  done  is  to 
make  plausible  guesses  as  to  what  the  procedure  really  was. 

The  modification  of  both  wild  and  domesticated  stocks 
through  hybridization  is  well  known  to  all  students  of 
hybridization,  and  these  modifications  are  of  two  general 
categories:  First,  the  production  of  new  combinations  of 
existing  attributes,  and  second,  the  origin  of  de  novo  varia- 
tions based  upon  the  attributes  of  the  crossed  stocks.  The 
first  is  by  far  the  most  common  change,  and  the  second 
is  relatively  rare  in  occurrence.  I  may  illustrate  the 
results  produced  in  these  two  kinds  of  modifications  by 
crossing,  by  examples  taken  from  my  cultures. 

L.  signaticollis  has  in  the  full-grown  larvae  one  row  of 
black  spots  on  the  dorsal  side,  with  a  deep  chrome-yellow 
body  color,  and  in  the  adult  the  elytra  are  marked  with 
irregular  rows  of  impressed  punctations  with  a  deposit  of 


Modification  of  Germinal  Constitution  of  Organisms       233 

black  pigment  at  the  bottom  of  each.  By  a  process  of 
hybridization  and  extraction  it  is  possible  to  obtain  a  race 
of  signaticollis  which,  if  found  in  nature,  would  be  regarded 
as  a  distinct  species;  and  when  it  occurs  in  experiment  it 
behaves  with  the  same  sharp  alternative  distinctness  of  any 
natural  species. 

If  a  female  of  L.  undecimlineata,  which  has  the  larval 
ground  color  white  without  any  black  spots  on  the  back, 
and  with  one  row  of  black  spots  surrounding  the  spiracles 
in  the  adult  larvae  and  the  impressed  punctations  very 
regular  in  pattern  with  the  rows  closely  parallel,  is  crossed 
with  a  male  of  L.  signaticollis,  the  F,  generation  gives  two 
types  of  larvae  (yls)  and  (whs},  in  the  proportion  of  1:1. 
From  the  (yls)  larvae  will  come  a  type  intermediate  between 
the  two,  and  this  type,  when  inbred,  gives  in  the  second 
hybrid  generation  four  types  of  full-grown  larvae  (whs), 
(whS),  (ylS),  and  (yls).  From  the  (whs)  larvae  in  the 
second  generation  are  obtained  three  classes  of  adults :  like 
the  female  parent,  L.  undecimlineata,  like  the  male  parent, 
L.  signaticollis,  and  intermediate  between  the  two. 

If,  now,  a  cross  be  made  between  these  extracted  F2  un- 
decimlineata types  with  the  extracted  F2  signaticollis  type, 
we  get  in  F3  mature  larvae  which  are  (whS),  and  these 
give  mid-type  adults  in  which  the  elytral  punctations  are 
arranged  in  closely  parallel  rows  like  the  undecimlineata 
type.  These,  when  inbred,  give  in  F4  larvae  which 
are  (whS)  like  the  undecimlineata  type,  and  these  larvae 
give  three  types  of  adults:  like  the  undecimlineata  type,  a 
mid-type,  and  like  the  signaticollis  type. 

The  signaticollis  type  which  comes  out  of  these  crosses 
is  the  modified  signaticollis  type,  and  these,  when  inbred, 
have  a  life  cycle  shorter  than  is  normal  to  signaticollis. 


234  Heredity  and  Eugenics 

Its  larval  stages  are  totally  different  from  the  larval  stages 
of  signaticollis,  and  the  general  appearance  of  the  organism 
is  totally  different.  This  type,  derived  from  these  variations 
by  a  series  of  hybrid  modifications,  if  placed  side  by  side  with 
the  normal  species  is  so  strikingly  different  that  if  found  in 
nature  no  one  would  hesitate  for  a  moment  to  designate  it 
a  distinct  Linnean  species.  Not  one  of  the  characters  in 
this  form  is  new,  and  each  is  directly  traceable  to  one  or 
the  other  of  the  parents — but  the  form  shows  a  new  arrange- 
ment of  these  attributes. 

In  this  species  a  germinal  modification,  obtained  through 
hybridization,  resulted,  in  which  a  rearrangement  of 
attributes  produced  new  combinations  which  are  stable 
under  the  conditions  of  existence.  It  cannot  be  said  in 
this  case  that  anything  new  has  been  produced,  only  that 
existing  characters  have  been  rearranged  and  produced  a 
combination  hitherto  unknown.  This  is  the  commoner 
type  of  modification  through  hybridization;  there  are,  how- 
ever, other  types  of  changes  which  are  still  more  interesting. 

3.     BY   COMBINED   SELECTIVE   CONCENTRATION  AND 
HYBRIDIZATION 

A  good  example  is  found  in  a  series  of  experiments 
recently  carried  out,  in  which  L.  undecimlineata  was  crossed 
with  L.  signaticollis  of  the  modified  419  stock,  but  with 
these  differences.  There  is  a  tendency  in  certain  races  of 
L.  undecimlineata  for  the  ramous  stripe  to  be  broken  about 
one-half  its  distance  from  the  anterior  end.  The  break  in 
this  stripe  is  fairly  common,  but  is  something  which  is 
not  really  fixed  in  this  species,  at  least  by  means  of  any 
known  process;  that  is,  it  cannot  be  rendered  a  permanent 
invariable  character,  but  a  race  can  be  created  in  which  the 


Modification  of  Germinal  Constitution  of  Organisms       235 

attribute  is  present  in  a  higher  proportion  of  individuals 
than  is  normal.  Such  a  race  was  created  by  means  of 
selection  in  which  about  60  per  cent  of  any  generation  would 
have  the  modification  and  the  other  40  per  cent  would 
be  without  it.  These  proportions,  however,  have  no  sig- 
nificance because  those  possessing  it  were  just  as  liable  not 
to  be  able  to  transmit  it,  and  those  that  did  not  possess  it 
were  just  as  likely  to  have  it  show  up  in  their  progeny. 

The  signaticollis  stock  had  further  been  modified  by  a 
selective  process  in  that  the  amount  of  black  pigment  upon 
the  impressed  punctations  had  been  considerably  increased 
and  by  selection  the  impressed  punctations  had  been 
brought  to  a  state  where  they  existed  in  irregular  parallel 
rows.  In  the  extreme  of  this  selected  stock  which  is  not 
constant,  the  appearance  of  the  elytra  is  often  that  of  two 
closely  placed  irregularly  parallel  black  lines.  There  is 
an  increase  of  pigment  which  finally  continued  from  one 
punctation  to  another,  making  a  continuous  line,  in  place 
of  a  series  of  broken  dots. 

These  two  stocks,  modified  by  selection,  were  crossed 
and  gave  in  the  first  hybrid  generation  two  types  of  adults: 
a  mid- type  and  one  like  the  female  undecimlineata  type. 
The  mid-type,  when  inbred,  gave  four  classes  of  full-grown 
larvae,  (whs),  (whS),  (jiS),  (yls),  and  from  each  of  these 
there  developed  three  classes  of  adults,  characteristic  of 
such  hybrid  operations.  In  the  three  classes  of  adults 
developed  from  the  (yls)  larvae  in  the  second  hybrid 
generations  are  found  a  variable  number  possessed  of  a 
combination  of  the  selected  characters  of  the  parents; 
that  is,  individuals  which  in  normal  crosses  are  of  the 
undecimlineata  type,  with  the  elytral  stripes  present  as 
one  single  solid  band,  in  this  cross  have  two  narrow 


236  Heredity  and  Eugenics 

parallel  bands.  A  double-striped  condition  in  place  of  a 
single  stripe. 

Many  of  the  mid-types  exhibited  the  same  modifica- 
tion to  a  lesser  degree,  especially  the  break  in  the  band. 
A  female  of  this  double-striped  character  was  mated  with 
an  extracted  male  undecimlineata  (a  brother),  and  when  in- 
bred there  were  obtained  in  the  next  generation  adults  with 
the  elytral  stripe  single,  the  elytral  stripes  single  and  broken, 
double,  double  and  broken.  From  these  it  has  been  pos- 
sible, by  a  process  of  analysis,  to  develop  the  following  stable 
combination :  a  type  in  which  the  larva  is  white  with  large 
black  spots  upon  the  back  like  the  larva  of  signaticollis,  but 
with  the  ground  color  white,  and  with  the  elytral  stripes 
double  in  the  adult;  the  same  type  with  the  stripes  double 
and  broken,  and  the  same  type  but  with  the  ramous  and 
first  costal  stripes  also  broken.  Third,  the  same  type  of 
larvae,  but  with  all  of  the  stripes  broken.  The  elytral 
stripes  are  extremely  invariable  and  most  difficult  of  modi- 
fication, but  this  example  shows  clearly  that  by  combining 
in  the  process  of  hybridization  characters  accentuated  by 
selection — and  it  will  probably  be  true  of  characters  accen- 
tuated in  any  other  way — that  there  is  a  definite  increase 
in  the  modification  of  characters  and  that  they  are  rendered 
stable  in  the  constitution  of  the  gamete  and  might  easily 
take  part  in  the  formation  of  species.  Figs.  J6A-G  show 
some  of  the  types  thus  far  obtained  from  an  evolution 
movement  initiated  by  the  process  described. 

In  these  experiments  the  modifications  are  in  no  wise 
due  to  the  influence  of  external  factors;  in  fact,  they  were 
carried  out  under  relatively  constant  conditions,  nor  is  it 
conceivable  that  external  factors  could  be  productive  of  such 
a  result.  What  it  is  that  has  brought  about  these  modifica- 


Modification  of  Germinal  Constitution  of  Organisms      237 


FIG.  76. — To  show  certain  new  types  that  have  recently  been  produced  by 
certain  processes. 


238  Heredity  and  Eugenics 

tions  we  have  no  means  of  knowing  until  more  is  known  of 
germinal  constitution.  It  is  clear,  however,  that  by  hybridi- 
zation it  is  possible  to  bring  about  permanent  modifications 
of  pattern,  and  these  are  not  only  modifications  of  color 
pattern  but  also  of  the  pattern  of  the  structures,  as  for 
example,  the  punctations,  venation,  etc.  These  latter 
attributes  are,  by  systematists,  considered  as  characters 
of  prime  importance,  and  are  made  the  basis  of  innumerable 
systematic  distinctions,  but  in  these  experiments  they 
are  as  susceptible  to  changes,  derangement,  and  de  novo 
variations  as  are  the  characters  which  are  based  upon  color, 
and  color  arrangement.  In  our  present  ignorance  of  the 
nature  of  the  localizing  process  in  any  material,  either  living 
or  non-living,  we  are  left  entirely  in  the  dark  as  to  what 
actually  goes  on.  The  experiments,  however,  suggest  the 
manner  in  which  modifications  may  result,  and  these 
resulting  modifications  may  well  be  productive  of  evolu- 
tion changes  either  of  advancement  or  regression. 

4.     BY    SELECTION 

DeVries  correctly  maintains  that  the  quantitative 
accumulation  of  small  variations  will  be  productive  of  a 
modification  which  will  move  rapidly  in  a  given  direction 
until  the  limit  is  reached.  This  can  be  demonstrated  in 
many  plants  and  animals  for  a  number  of  characters.  The 
manner  in  which  quantitative  accumulation  operates  is 
well  shown  by  the  following  examples: 

I  attempted  by  selection  to  create  an  albinic  race  of  L.  decemlineata 
in  two  ways — first,  by  selecting  for  breeding  the  most  extreme  albinic 
variations  found  in  nature,  and  second,  by  creating  extreme  albinic  con- 
ditions in  experiment  and  breeding  from  them.  For  the  first  set 
of  experiments  the  selection  was  made  from  numbers  of  copulating 


Modification  of  Germinal  Constitution  of  Organisms      239 

pairs  found  in  nature.  The  selected  pairs  were  kept  in  separate  cages, 
as  were  their  progeny,  the  only  lumping  of  material  being  in  the  statis- 
tical treatment  of  it.  The  great  majority  of  such  pairs  and  their  off- 
spring were  not  of  any  interest.  Out  of  311  pairs  selected  and  mated 
in  the  years  1896-1904,  only  26,  or  8^  per  cent  of  the  total  number  of 
paks  tried,  were  found  capable  of  transmitting  their  particular  varia- 
tions. In  many  of  these  pairs  it  was  certain  that  only  one  of  the 
beetles  had  the  character  in  transmissible  form,  so  that  in  311  pairs, 
or  622  individuals,  the  actual  percentage  of  specimens  showing  heritable 
variations  was  probably  not  far  from  4  or  5  per  cent. 

Starting  from  a  single  pair  of  albinic  individuals  hi  which  the  selected 
character  was  transmissible,  and  following  the  line  of  descent  from 
generation  to  generation,  the  fact  is  graphically  shown  in  Fig.  77  that 
the  particular  variation  of  the  parent  was  not  only  preserved,  but 
carried  close  to  the  limit  of  normal  variability  of  the  species,  and  that 
by  selection  the  race  was  changed  from  one  which  was  variable  to  one 
which  was  relatively  invariable — that  is,  selection  resulted  hi  the  pro- 
duction of  a  race  of  albinic  beetles  of  low  variability,  which,  no  doubt, 
it  would  have  been  easy  to  maintain  for  a  long  period  of  tune.  From 
the  third  generation  a  selection  was  made  for  the  parents  of  the  fourth  of 
the  most  and  least  albinic  individuals,  (A)  still  being  the  albinic  race 
and  (B)  the  divergent  race  tending  toward  the  opposite  extreme.  These 
two  lots  of  parents  gave  in  the  fourth  generation  two  distinct  polygons 
which  overlapped,  only  in  the  slightest  extent.  By  continued  selection 
the  polygons  in  the  fifth  generation  did  not  overlap,  and  hi  this  genera- 
tion further  division  was  made  of  (B)  into  (B)  and  (C).  These  two 
lines  were  continued  for  several  generations,  diverging  from  the  (A) 
line,  but  not  far  nor  rapidly.  In  the  second  generation  there  arose 
two  distinct  groups  separated  by  a  wide  gap  (A)  and  (D),  the  latter 
being  the  exact  opposite  of  the  (A)  race.  This  (D)  race  was  propa- 
gated, and  by  selection  produced  the  result  shown  in  the  polygons 
along  the  line  of  descent  (D),  giving  in  the  last  generation  of  the  race  a 
group  of  beetles  of  almost  uniform  condition.  In  all  the  lines  of  descent 
(A),  (B),  (C),  and  (D),  artificial  selection  did  just  what  it  was  found  to 
do  hi  the  elements  of  coloration,  namely,  it  created  a  race  of  low  vari- 
ability about  the  standard  chosen  which  it  maintained  as  long  as  selec- 
tion was  practiced;  but  it  did  not  carry  the  race  beyond  the  normal 


240 


Heredity  and  Eugenics 


'Normal"  range  of  variation. 
Mode. 


FIG.  77. — Diagrammatic  representation  of  the  results  obtained  in  the  effort 
to  create  albinic  and  melanic  races  by  selection.  Shows  also  the  inability  of  quanti- 
tative accumulations  to  carry  the  modification  beyond  the  normal  range  of 
variation,  and  also  the  rapidity  with  which  races  so  created  revert  to  the  normal 
standard  when  the  selective  influence  is  removed. 


Modification  of  Germinal  Constitution  of  Organisms      241 


'Normal"  range  or  variation. 


FIG.  78. — Diagrammatic  representation  of  the  results  obtained  in  the  creation 
of  races  by  selection  of  variations  capable  of  transmission. 


242  Heredity  and  Eugenics 

range  of  variation  of  the  species.  That  is,  artificial  selection  can,  as 
DeVries  points  out,  produce  races  and  maintain  them,  but  its  power 
to  develop  these  races  beyond  the  natural  range  of  variability  is  yet 
to  be  demonstrated. 

From  the  series  of  cultures  represented  in  Fig.  77,  it  is  shown  that 
it  is  easy  by  selection  to  create  races  from  a  species,  which  would  as 
long  as  the  artificial  selection  lasted,  breed  true  to  the  ideal  chosen. 
Another  such  an  experiment  and  two  races  breeding  true  that  were 
produced  are  represented  in  Fig.  78.  From  the  parent  generation  two 
selected  groups,  one  melanic  (B),  the  other  albinic  (A),  were  taken, 
and  from  these,  two  clearly  defined  races  without  trace  of  intermediate 
condition  were  produced.  During  each  of  eight  consecutive  genera- 
tions slightly  variable,  light  and  dark  races  were  maintained.  At  the 
end  of  this  time  the  material  was  divided  and  selection  was  stopped 
in  one  group  and  continued  in  the  other,  but  the  lots  were  not  allowed 
to  interbreed.  The  removal  of  the  selective  factor  at  once  resulted  in 
a  regressive  shifting  of  the  mode  of  each  unselected  race  and  in 
increased  variability,  and  this  change  continued  through  the  eleventh 
generation,  when  both  unselected  lots  had  moved  back  to  the  mode  of 
the  species. 

These  experiments  with  color  characters  show  very  clearly  that 
artificial  selection  is  with  transmissible  variations  a  powerful  factor 
and  can  greatly  accentuate  any  character  and  maintain  it  in  an 
extreme  condition,  but  that  there  are  limits  beyond  which  I  was 
not  able  to  modify  the  characters  by  this  agency.  The  experiments 
also  show  that  artificial  selection  works  rapidly,  and  not,  as  has  been 
so  often  assumed,  with  extreme  slowness.  True,  in  experiment  I 
practiced  a  most  rigorous  selection,  but  not  more  rigorous  than  that 
which  the  natural  selectionists  believe  exists  in  nature. 

The  experimental  production  of  general  color  variations  and  their 
preservation  by  selective  breeding  give  many  points  of  interest.  In 
this  I  have  confined  my  attention  almost  entirely  to  extreme  light 
and  dark  forms.  To  produce  light  forms  I  have  used  hot  and  dry 
conditions,  and  for  dark  forms  warm  and  moist.  The  experiments 
herein  recorded  differ  from  those  already  given  in  that  the  entire  life 
of  the  beetles  was  passed  in  the  conditions  of  the  experiment,  and 
not  the  larval  and  pupal  stages  alone  as  in  the  experiments  upon 
coloration. 


Modification  of  Germinal  Constitution  of  Organisms      243 


'Normal  Range  of  Variation" 


Classes  23  22  21  20  19  18  17  16  15  14-  13  12  II  10  9  8   7654324   a.  b.  a  d.  e.  f  £.  h. 


FIG.  79. — Diagrammatic  representation  of  the  results  obtained  in  the  creation 
of  albinic  and  melanic  races  by  the  combined  influence  of  selection  and  environ- 
mental stimuli.  These  experiments  show  a  difference  from  the  results  shown  in 
some  of  the  former  diagrams,  in  that  there  are  a  number  of  extreme  variations 
produced  which  apparently  are  stable  in  several  successive  generations;  however, 
when  the  selective  effect  is  removed  the  divergent  race  is  seen  not  to  be  stable  and 
to  revert  with  considerable  rapidity  to  the  mediocre  or  parental  stock. 


244  Heredity  and  Eugenics 

In  Fig.  79  are  brought  together  in  diagrammatic  form  the  data 
and  general  history  of  cultures  where  both  light  and  dark  forms  were 
produced  and  further  subjected  to  experiment.  The  black  polygons 
represent  the  selected  groups  of  parents,  the  ruled  polygons,  the 
offspring.  The  appearance  of  "mutants"'  beyond  the  normal  range 

of  variability  is  indicated  by  the  small  white  polygons The 

series  is  a  complex  one,  involving  processes  other  than  artificial 
selection  and  introducing  factors  of  interest  which  are  the  key  to 
further  experimental  study.  At  present  only  that  portion  directly 
concerned  with  selection  or  selective  processes  need  be  considered. 

In  the  first,  or  parent,  generation  I  selected  6  copulating  pairs  of 
beetles  from  the  hibernating  population,  and  kept  them  and  their 
progeny  in  natural  conditions.  From  the  6  pairs  were  obtained  in 
the  second  generation  1,320  mature  beetles,  and  from  these,  two 
groups  of  copulating  pah's  of  10  each  (A  and  B)  were  selected  and 
reared  hi  the  third  generation,  but  showed  no  modifications  as  the 
result  of  selection.  These  hibernated,  and  selections  from  each  lot 
were  reared  in  the  fourth  generation,  but  showed  no  modification. 
I  now  felt  sure  that  the  material  was  pure,  that  is,  normal,  and  carried 
no  tendencies  to  appear  in  divergent  extreme  variations.  Accord- 
ingly, from  the  two  series  selection  was  made  of  as  nearly  modal 
individuals  as  possible,  and  the  two  selected  lots  were  mixed  and 
divided  into  two  lots  of  10  pairs  each  (C)  and  (D).  These  were 
placed,  as  soon  as  possible  after  emerging,  in  surroundings  produc- 
tive of  dark  and  light  conditions  of  coloration,  and  allowed  to  breed, 
producing  in  the  fifth  generation  two  distinct  lots  of  descendants, 
one  light,  the  other  dark.  These  hibernated,  and  after  emerging 
in  the  following  spring  were  allowed  to  breed,  when  it  was  found  that 
out  of  50  mated  pairs  31,  or  62  per  cent,  were  able  to  transmit  their 
particular  variations  in  full  strength,  a  huge  increase  over  that 
found  in  selections  from  nature.  From  each  group  5  pairs  were 
selected  as  the  parents  of  the  sixth  generation.  These  gave,  as  was 
expected,  distinct  lots  of  individuals  more  melanic  and  more  albinic 
than  their  parents,  and  each  also  produced  individuals  differing  in 
many  respects  from  the  parent  stock,  and  beyond  the  usual  range  of 
variability.  In  the  five  following  generations  the  same  thing  was 
repeated,  as  may  be  seen  from  Fig.  79;  that  is,  from  each  group  of 


Modification  of  Germinal  Constitution  of  Organisms       245 

selected  parents  there  came  a  general  population  less  and  less  variable, 
and  a  greater  or  less  number  of  highly  divergent  forms  beyond  the 
normal  range  of  variability  of  the  species.  These  latter  we  shall 
consider  in  another  place. 

In  this  series  of  cultures  a.  normal  parent  stock  has  been  subjected 
to  artificial  selection  aided  by  powerful  environmental  stimuli,  both 
having  the  production  of  the  same  end  in  view.  The  results,  however, 
were  a  keen  disappointment ;  the  inability  to  produce  by  selection  and 
powerful  environmental  influences  a  race  much  beyond  the  normal 
limits  of  variability  of  the  species  might  easily  be  taken  to  indicate 
the  impotency  of  selection.  The  ease  with  which  the  beetles  moved 
back  toward  the  mode  when  selection  was  no  longer  practiced  and 
the  conditions  of  existence  became  modal,  when  joined  to  the  data 
of  place  and  geographical  variations,  allows  only  of  the  conclusion 
that  while  differently  colored  races  and  modifications  of  this  organ- 
ism occur  in  nature  and  are  produced  in  experiment  by  artificial 
selective  processes  and  local  environmental  influences,  such  modi- 
fications are  limited  by  the  natural  limits  of  variation  of  the  species 
and  persist  only  as  long  as  the  maintaining  processes  are  present 
and  are  utterly  incapable  of  existence  under  adverse  conditions, 
reverting  to  the  species  type.  That  is,  artificial  selections  or  local 
influences  are  able  to  modify,  and  to  a  certain  extent  create,  races 
founded  upon  those  variations  which  are  ordinarily  killed  off  by 
natural  selection;  but  in  the  creation  of  such  races  we  really  have 
two  forces — a  species  tendency  and  a  local  (or  artificial  in  experiment) 
— acting  against  one  another,  with  the  result  that  selective  divergence 
to  a  certain  limit  is  attained,  but  beyond  that  the  racial  divergence  is 
slow  or  entirely  stopped.  When  the  local  or  artificial  selection  is  re- 
moved the  species  selective  tendency  causes  a  regression  to  the  type 
of  the  species.  It  may  be  objected  that  my  experiments  do  not  cover 
a  sufficiently  long  series  of  generations  to  have  accomplished  the 
result  intended,  and  this  may  be  true;  but  selection  is  a  powerful 
formative  factor  and  works  rapidly  up  to  a  certain  limit,  and  this  has 
been  abundantly  proven  by  plant  and  animal  breeding  for  fifty  years. 
Why  should  it  not  also  be  able  to  establish  a  race  on  permanent 
footing  with  the  same  rapidity  ?  It  is  known  from  the  rearing  of 
domestic  animals  and  plants  that  constant  selection  is  necessary 


246  Heredity  and  Eugenics 

to  maintain  the  race.  In  so  far  as  color  characters  are  concerned, 
by  artificial  selection  we  can  easily  produce  and  maintain  a  race,  but 
cannot  establish  it  as  an  independent  one;  it  is  possible  to  create 
isolated  races  from  extreme  variations,  and  by  selection  keep  them 
isolated,  but  it  seems  very  difficult  to  permanently  establish  them. 
On  the  whole,  selection  would  appear  as  a  relatively  impotent  factor 
in  evolution.  Two  points  should  be  noted,  in  passing,  namely,  the 
number  of  highly  divergent  variations  beyond  the  normal  range  of 
fluctuating  variation  produced  in  this  last  series  of  experiments,  and 
the  increased  percentage  of  individuals  which  show  variations  capable 
of  being  transmitted  to  the  progeny. 

It  seems  to  be  a  well-established  fact  that  by  quanti- 
tative accumulation,  pigment  or  any  other  character  in  the 
organism  can  be  made  to  diverge  rapidly  up  to  a  certain 
limit,  beyond  which  it  is  practically  impossible  to  go.  More 
striking,  however,  is  the  rapidity  with  which  such  races 
revert  to  the  modal  condition  of  the  parent  stock  when 
the  selective  process  has  ceased.  This  phenomenon  has 
been  characterized  as  regression  toward  the  mean,  and 
it  may  represent  either  one  of  two  processes — an  inherent 
tendency  in  the  organism  to  revert  to  the  standard,  or  it 
may  represent  a  selective  process  which  goes  on  within  the 
organism.  I  am  of  the  opinion  that  the  latter  is  the  correct 
explanation  of  this,  for  the  following  reason:  modification 
by  the  quantitative  accumulation  of  minute  fluctuating 
variations  is  always  working  against  what  may  be  termed 
the  natural  selective  tendency,  that  is,  against  those  tend- 
encies which  surround  every  organism  and  which  eliminate 
extremes  in  each  generation  through  one  cause  or  another, 
allowing  the  modal  type  to  persist.  Any  effort,  therefore, 
to  preserve  the  extreme  type  comes  in  conflict  with  that 
which  serves  to  eliminate  extremes  and  preserve  the  modal 
type.  There  are  two  conflicting  forces,  one  which  tends 


Modification  of  Germinal  Constitution  of  Organisms      247 

to  preserve  the  extreme  and  by  rigorous  selection  to  eliminate 
the  mean,  and  the  other  which  tends  to  eliminate  the 
extreme  and  preserve  the  mean.  Rigorous  artificial  selec- 
tion makes  the  preservation  of  the  extreme  the  more  potent 
of  the  two,  and  results  in  rapid  divergence,  but  not  in 
unlimited  divergence,  and  when  this  selective  process  ceases 
the  natural  selective  process  again  becomes  operative  with 
the  result  that  there  is  rapid  regression  to  the  mean  racial 
standard. 

Confusion  exists  in  many  records  of  selection  experi- 
ments, due  to  the  presence  of  biotypes  or  phenotypes,  so 
that  the  selection  is  really  a  process  of  separating  the  present 
elemental  forms.  In  the  above-cited  experiments  only  one 
biotype  was  present  and  this  was  not  capable  of  being 
changed  by  selection — quantitative — beyond  the  normal 
range.  The  bearing  and  necessity  of  working  with  one 
biotype  in  this  selection  work  and  not  with  a  complex  of 
several  is  well  known  to  all  students  of  genetics  at  the  present 
day,  although  not  adequately  appreciated  by  practical 
breeders. 

The  facts  concerning  inconstancy  and  reversion  are  well 
known  to  breeders  of  animals  and  plants,  who  must  practice 
constant  selection  to  maintain  the  standard  of  their  artifi- 
cially improved  races.  Is  it  possible  to  produce,  by  a  selective 
process,  modifications  which  are  permanent  and  which  do 
not  revert  on  the  cessation  of  the  selective  action,  which 
maintain  themselves  when  brought  in  contact  with  the 
parent  species,  and  which  maintain  themselves  when  placed 
in  nature?  In  selective  processes  of  this  kind,  amount 
is  a  negligible  quantity;  only  pattern  arrangement  need  be 
considered.  In  other  words,  those  differences  in  the  consti- 
tution of  the  organism  which  localize  specific  characters 


248  Heredity  and  Eugenics 

in  definite  areas  can  be  acted  upon  by  selective  combinations 
to  produce  permanent  results.  One  example  will  serve  to 
illustrate  this. 

Material  of  L.  signaticollis  Stal,  a  specific  form  limited 
to  a  narrow  habitat  in  nature,  and  of  low  variability  in  all 
of  its  characters,  was  the  basis  of  this  experiment  in  selec- 
tion. Compared  with  other  members  of  the  genus  with 
which  it  is  closely  related,  the  variations  of  L.  signaticollis 
are  trivial,  so  that  one  would  on  a-priori  grounds  be  certain 
to  regard  it  as  a  hopeless  task  to  attempt  with  L.  signati- 
collis studies  in  experimental  evolution  by  selective  methods. 
By  a  process  of  combining  variations  in  the  pattern  of  the 
pronotum  it  is  possible  through  a  series  of  generations  to 
create  a  type  of  pattern  permanent  in  all  respects,  and  which 
behaves,  when  crossed  with  other  patterns,  with  all  the 
sharp  alternativeness  of  characters  found  in  nature. 

The  selection  was  begun  in  the  ninth  generation  of  the 
stock  which  had  been  bred  as  group  cultures  and  as  pedigree 
cultures  and  had  never  shown  the  modifications  which 
were  produced;  further,  the  modifications  produced  are 
not  known  to  exist  in  nature.  In  the  F9  generation,  a 
combination  was  made  of  the  pronotal  pattern,  and  from  this 
there  arose  a  variable  progeny,  F10.  From  generation  FIO, 
matings  were  made  and  during  generations  Flf,  FI2,  FI3, 
FI4,  FIS,  and  Fl6,  etc.,  the  combinations  were  made  from 
generation  to  generation,  with  the  end  result  that  there 
has  been  developed  a  permanent  strain,  which  since  the 
FI2  of  FI3  generation  has  remained  stable.  In  this  strain 
the  spots  are  all  fused  into  one  solid  mass  and  are  carried 
backward  until  they  completely  border  the  posterior  edge 
of  the  pronotum,  and  anteriorly  to  the  anterior  edge  and 
laterally,  leaving  only  a  small  border  unpigmented.  Such  a 


Modification  of  Germinal  Constitution  of  Organisms       249 

combination  is  not  known  in  nature,  but  there  has  twice 
appeared  in  my  cultures  a  somewhat  similar  variation  which 
could  be  classed  as  a  sport,  which  variations,  however 
always  failed  to  perpetuate  themselves. 

These  cultures  are  able  to  maintain  themselves  under  the 
conditions  of  the  vivarium  in  both  group  and  pedigree 
cultures  without  further  attention,  or  attempts  to  main- 
tain the  race.  More  interesting,  however,  is  the  behavior 
of  these  modified  forms  when  placed  in  nature  in  their 
normal  habitat,  where  they  have  maintained  themselves 
with  undiminished  attributes,  and  there  has  not  been  the 
slightest  indication  of  reverting  to  the  ancestral  state. 
When  material  of  this  type  is  crossed  with  material  of  the 
parental  stock  obtained  from  the  original  locality,  the 
modified  attribute  behaves  as  a  striking  dominant  alternative 
characteristic. 

Of  further  interest  is  the  ontogenetic  series  of  events  in 
the  development  of  this  modified  color  pattern.  In  this 
instance  I  know  step  by  step  exactly  what  went  into  the 
combination,  also  what  the  ontogenetic  sequence  of  events 
was  in  each  type  of  parent,  and  it  is  naturally  expected  that 
the  modifications  would  present  a  series  of  ontogenetic 
stages  one  following  the  other,  and  that  the  ontogeny  of 
these  modified  individuals  should  rather  closely  recapitulate 
the  recent  events  which  the  organism  has  gone  through  in 
attaining  its  present  state.  This  is  exactly  what  the  organ- 
ism does  not  do.  Like  any  well-regulated  physico-chemical 
mechanism  it  cuts  out  the  non-essential  and  takes  the  short- 
est cut  to  attain  its  present  end.  This  short  cut,  wherein 
stages  which  it  passes  through  in  its  phylogenetic  develop- 
ment are  left  out,  and  where  many  characters  are  lost  com- 
pletely, shows  that  in  this  instance  a  modified  pattern  has 


250  Heredity  and  Eugenics 

arisen  by  an  accumulative  process,  giving  all  the  same 
permanence  and  strength  of  character  as  is  found  in  what 
are  called  natural  species  or  characters. 

The  same  process  has  been  applied  to  other  forms  and 
attributes  with  identical  results,  the  only  limitations  being 
such  as  are  imposed  by  the  physical  constitution  of  the 
organism  itself,  or  of  the  part  in  which  the  modification  is 
being  carried  on,  so  that  a  character  might  become  after  a 
time  decidedly  injurious  in  the  economy  of  the  species  and 
therefore  come  under  the  operation  of  natural  elimination. 
This  pattern,  however,  is  a  neutral  character  and  the  only 
limitation  is  that  imposed  by  the  physical  constitution  of 
the  part  and  there  is  apparently  no  direction  in  which  the 
modification  must  never  go. 

In  another  series  derived  from  the  original  stock,  modifi- 
cations were  carried  out  in  the  reverse  of  this  one,  producing 
a  stock  in  which  all  of  the  spots  were  reduced  to  round  simple 
areas  with  absolutely  no  tendency  to  fusion  or  breaking  up 
of  the  spots  into  many  tributary  rows.  From  these  experi- 
ments two  points  are  clearly  demonstrated:  First,  it  is 
shown  that  a  selective  process  may  permanently  modify 
one  of  the  most  inflexible  of  characters,  namely,  pattern, 
and  this  modification  may  even  greatly  exceed  any  of  the 
variations  known  in  the  species.  This  selective  process  is 
different  from  the  quantitative  accumulation  which  has 
been  employed  by  plant  and  animal  breeders.  It  is  not  a 
process  of  hybridization,  but  is  analogous  to  the  processes 
which  a  chemist  would  use  in  synthetizing  a  complex  com- 
pound, adding  to  it  first  one  thing,  then  another,  subtracting 
from  this  a  product,  then  adding  to  it  some  more,  until  the 
end  product  is  totally  different  from  the  original  material. 
It  is  a  process  of  synthesis  and  not  of  accumulation. 


Modification  of  Germinal  Constitution  of  Organisms       251 

The  second  observation  has  a  bearing  upon  the  current 
theories  of  biogenesis  and  orthogenesis,  showing  the  distinct 
failure  of  this  modified  organism  to  repeat  in  its  ontogeny 
the  stages  which  it  has  recently  passed  through  in  its 
phylogenetic  development.  It  has  long  been  maintained, 
from  a  paleontological  standpoint,  and  from  study  of  the 
ontogeny  of  an  organism,  that  the  stages  passed  through 
represent  a  recapitulation  of  the  more  essential  stages  of  its 
recent  development.  Jackson  on  paleozoic  echini,  Hyatt 
on  ammonites,  and  Beecher  on  brachiopods  have  shown 
that  there  is  a  constant  dropping  of  the  earlier  and  more 
primitive  stages  in  the  ontogeny  of  a  species,  and  a  reduc- 
tion of  the  later  stages.  There  is  of  course  a  large  amount 
of  permanent  truth  in  the  view  obtained  from  these  paleon- 
tological studies,  that  the  organism  recapitulates  its  phylo- 
geny,  at  least  to  a  greater  or  less  extent,  but  it  is  equally 
true  that  the  literal  interpretation  of  this — the  utilization 
of  the  ontogenetic  stages  as  a  test  in  determining  relation- 
ships and  direction  of  evolution — is  futile. 

It  would  be  difficult  to  interpret  a  case  like  the  one 
given  on  any  other  basis  than  that  used — that  the  conditions 
found  represent  the  best  adjustment  which  the  physico- 
chemical  mechanism  could  possibly  achieve  in  order  to 
attain  a  definite  end.  To  do  this,  instead  of  following  an 
irregular  and  complex  path,  it  cuts  straight  across,  elimi- 
nating minor  steps  which  have  played  a  phylogenetic  role 
but  have  no  part  in  the  achievement  of  the  final  end  result 
in  the  ontogeny  of  the  parent  stock. 

It  has  been  maintained  that  evolution  is  irreversible 
and  that  once  started  it  must  continue  to  the  end.  It  is 
difficult  to  conceive  of  any  reason  why  this  should  be  so 
unless  there  be  assumed  the  existence  of  an  inherent  force 


252  Heredity  and  Eugenics 

or  cause  driving  organisms  toward  a  series  of  goals,  which, 
when  passed,  represent  the  final  goal  of  that  particular  race. 
If  this  conception  were  true,  then  there  would  exist  in 
organisms  a  state  totally  unlike  that  found  elsewhere  in 
nature.  In  no  physical  or  chemical  phenomena  does  any 
such  condition  exist,  but  rather,  an  array  of  substances 
which  can  be  combined  and  recombined  in  an  almost  infinite 
series  of  combinations,  which  can  be  built  up  to  complex 
aggregations  and  with  equal  facility  reduced  down  to  the 
atomic  groups  from  which  they  came.  In  other  words, 
by  a  selective  synthetic  process  it  is  possible  to  create  or 
synthetize,  and  likewise,  by  a  selective  analytical  process 
to  analyze,  and  the  irreversibility  of  evolution  exists  only 
in  the  dogmatism  of  some  essayists,  and  not  in  the 
materials  of  nature. 

To  what  extent  the  selective  process  is  operative  in  the 
production  of  variation  in  nature  is  unknown.  It  is  not 
probable  that  in  nature  there  would  exist  the  arrangement 
of  variations  which  I  brought  about  in  experiment,  but  in 
nature  I  should  rather  look  for  a  very  decidedly  haphazard 
process,  bringing  about  chance  combinations  which  would 
produce  this  or  that  result,  and  these  chance  combinations 
might  any  two  of  them  combine  and  produce  a  third  chance 
combination  which  would  stand  apart  from  the  parent 
species — the  product  of  the  two  others,  but  if  found  in 
nature  it  would  be  described  as  a  "mutation."  What  role 
these  variations,  and  I  am  convinced  that  they  are  potent 
factors  in  evolution,  really  would  have  in  the  general  evolu- 
tion of  organisms  and  in  the  development  of  species,  is  un- 
known. It  is  not  inconceivable  that  a  variation  might 
thus  arise  which,  behaving  as  a  strong  dominant  or  as  a 
dominant  heterozygote,  could  increase  in  numbers  and 


Modification  of  Germinal  Constitution  of  Organisms       253 

after  a  time  replace  the  parent  species  to  a  considerable 
extent,  if  not  completely. 

C.     Discussion — Summary 

Probably  no  question  in  biology  has  received  more 
attention,  and  certainly  few  are  so  little  understood,  as  the 
method  whereby  those  variations  which  are  productive  of 
permanent  change  arise  and  become  incorporated  into  the 
germinal  constitution  of  the  race.  If  the  possibility  of 
variations  arising  in  a  manner  like  that  assumed  in  the 
neo-Lamarckian  conception  be  admitted,  it  must  also  be 
admitted  that  there  is  at  present  no  critical  evidence  of  any 
such  method  of  origin.  As  far  as  experience  warrants  a 
conclusion,  there  is  at  present  no  escape  from  the  general 
proposition  that  all  variations  that  are  productive  of  per- 
manent germinal  changes,  arise  primarily  in  the  germ  and 
appear  secondarily  in  the  soma.  It  must  be  understood 
that  by  this  proposition  it  is  not  asserted  that  it  is  the  only 
possible  conception,  but  that  it  is  the  only  one  concerning 
which  there  is  at  the  present  time  any  definite  proof. 

Knowledge  concerning  the  germ  cells,  which  are  the 
germ  plasm  or  else  the  carriers  of  it,  is  largely  anatomical  in 
character,  derived  from  studies  in  cytology  and  in  the  main 
is  one  sided,  incomplete,  and  has  been  too  much  directed  to 
the  study  of  the  chromosomes.  That  this  is  the  condition 
is  not  strange  when  one  considers  the  wonderful  regularity 
with  which  the  chromosomes  are  divided  between  the 
daughter  cells,  and  the  precision  and  regularity  of  the  process 
immediately  preceding  and  accompanying  fertilization. 
These  phenomena,  so  fundamental  and  common  to  all 
organisms,  have  impressed  biologists  profoundly  and  very 
naturally  the  opinion  arose  that  the  chromosomes  were  the 


254  Heredity  and  Eugenics 

bearers  of  that  which  conditions  the  characteristics  of  the 
subsequent  generation.  Recent  cytological  studies,  how- 
ever, have  demonstrated  that  the  early  conception  of 
equality  in  the  distribution  of  the  chromosomes  is  not 
entirely  true,  but  that  there  is  a  regular  and  unequal  dis- 
tribution of  the  chromosomes  which  occurs  in  many,  if 
not  all  animals,  producing  in  some  two  classes  of  ova,  in 
other  instances  two  classes  of  spermatozoa. 

These  chromosomal  differences  in  some  unknown  manner 
are  now  generally  admitted  to  be  associated  with  the 
determination  of  sex;  hence  the  "accessory  chromosomes" 
which  go  to  make  chromosomal  differences  in  the  germ 
cells  are  regarded  by  some  as  sex  determinants.  That  they 
are  sex  determinants  in  the  sense  in  which  "determined" 
has  been  used  is  not  proven.  The  results  obtained  by 
Morgan  in  Phylloxera  seem  crucial  and  show  that  the  extra 
chromosomes  are  an  accompaniment  of  differentiation,  and 
not  the  cause  thereof.  At  any  rate  it  is  definitely  proven 
that  the  existence  of  the  accessory  chromosomes  represents 
a  definite  difference  in  the  qualities  and  constitution  of  the 
germ  cells,  and  thus  gives  in  gametogenesis  germ  cells 
differing  from  one  another  by  sharp  alternative  differences. 
There  is  no  a-priori  reason  why  the  same  may  not  be  true  of 
attributes  and  qualities  in  the  germ  cell  which  are  not 
capable  of  observation  by  present  cytological  methods. 

In  the  last  decade  the  work  of  many  investigators,  but 
especially  that  of  Conklin,  Lillie,  Morgan,  Driesch,  and 
Wilson,  has  shown  that  the  germ  cells  are  in  reality  highly 
complex  structurally,  possessing  a  definite  organization 
and  polarity,  with  a  distribution  of  various  elaborated  sub- 
stances which  are  individually  more  or  less  necessary  to  the 
proper  development  of  particular  parts  of  the  future  embryo. 


Modification  of  Germinal  Constitution  of  Organisms       255 

It  is  clearly  shown  that  in  the  germ  cell  before  fertilization 
there  is  a  fundamental  symmetry,  polarity,  from  which  there 
arise  during  ontogeny  the  symmetries  and  arrangements 
existing  in  the  developing  individual.  This  symmetry, 
as  far  as  there  is  any  evidence,  continues  back  through  all 
the  cell  generations  which  arise  during  gametogenesis, 
and  on  the  basis  of  what  is  known  of  development  in  the 
germ  cell,  it  seems  to  be  a  symmetry  directly  derived  from 
the  parent  zygote.  In  other  words,  in  the  continuity  of 
the  germ  cells  from  generation  to  generation,  there  is  a 
continuity  of  the  symmetries  and  physical  constitution 
characteristic  of  the  germinal  material,  a  continuity  of 
germinal  organization.  It  seems  clearly  established,  espe- 
cially by  the  work  of  Lillie  and  Morgan,  that  there  is  a 
fundamental  background,  or  matrix,  in  the  germ  cell  in 
which  the  original  symmetries  are  expressed.  For  the  pres- 
ent the  entire  germ  cell  must  be  regarded  as  the  germinal 
material  or  germ  plasm,  and  our  problem  in  the  investiga- 
tion of  the  origin  of  germinal  variations  is  to  discover 
by  what  methods  changes  in  the  germ  cells  are  brought 
about.  This  is  one  of  the  most  difficult  problems  con- 
fronting biologists,  and  one  which  is  possibly  incapable  of 
solution,  at  least  in  the  near  future,  and  perhaps  may 
forever  remain  unsolved. 

The  chemical  changes  which  go  on  in  the  living  sub- 
stance, especially  those  which  follow  in  the  metabolism  of 
organisms,  have  been  roughly  outlined,  but  these  metabolic 
processes,  while  they  may  result  in  the  elaboration  of  pro- 
ducts to  be  incorporated  into  or  removed  from  the  organism 
in  one  way  or  another,  do  not  possess  any  capacity  for 
carrying  on  their  operations  excepting  in  the  living  mass. 
Moreover,  we  understand  in  a  broad  way  the  mechanical 


256  Heredity  and  Eugenics 

and  physical  principles  involved  in  the  passage  of  fluids 
from  one  part  to  another  or  to  the  outside,  and  something 
of  the  role  which  katalytic  changes  play  in  organic  activi- 
ties. The  time  has  not  come  when  this  information  can  be 
directly  applied  to  the  problem  of  the  chemical  nature  of 
germinal  changes. 

As  regards  form  and  pattern,  the  biologist  is  confronted 
in  organisms  with  the  same  difficulties  as  are  presented  to  the 
physicist  and  chemist  to  explain  form  and  pattern  in  non- 
living substances.  No  physicist  would  presume  to  say  what 
it  is  in  the  composition  of  a  crystal  which  makes  so  definitely 
for  a  specific  form  of  face,  hardness,  and  optical  properties. 
The  problem  is  the  same  in  both  living  and  non-living 
substance,  and  the  forces  which  determine  form  and  pattern 
seem  to  be  properties  of  the  entire  mass  and  are  not  local- 
ized, and  are  probably  produced  in  organisms,  as  in  non- 
living masses,  by  the  sum  total  of  the  interactivities  of 
the  mass  at  the  moment  of  observation. 

In  every  part  of  the  organism  there  is  a  symmetry  which 
is  the  outgrowth  of  the  original  symmetry  from  which  the 
organism  developed.  Variations  in  the  secondary  or  later 
symmetries  may  be  large,  but  almost  never  are  there 
variations  in  the  fundamental  symmetries  which  distinguish 
phyla.  Evolution  is  mainly  concerned  in  the  problem  of 
the  formation  of  species  or  attributes  with  variations  in 
these  secondary  symmetries  and  patterns.  I  have  shown 
how  certain  of  these  symmetries  may  be  modified. 

Not  the  slightest  clue  of  what  it  is  that  is  modified  in  the 
germ  cells  of  a  particular  species  as  the  result  of  any  modi- 
fying process  has  been  recorded,  and  the  usual  attempted 
explanations  are  based  upon  assumed  a-priori  conceptions, 
usually  atomistic  in  character,  on  the  order  of  Darwin's 


Modification  of  Germinal  Constitution  of  Organisms       257 

provisional  hypothesis  of  pangenesis,  the  id-determinant- 
biophore  fabric  of  Weismann,  or  the  pangene  complex  of 
DeVries.  Much  has  been  written  concerning  the  uselessness 
of  such  conceptions  as  explanations;  much  has  been 
written  in  their  favor,  and  the  only  truthful  statement 
possible  is  that  there  is  no  evidence  for  their  existence. 
The  important  contribution  is  the  experimental  evidence 
showing  that  the  symmetries  and  patterns  in  organisms  are 
definitely  modifiable  as  the  result  of  synthetic  and  other 
processes  which  may  be  carried  on  under  observation,  and 
which  achieve  definite  results.  In  most  instances  thus  far 
recorded  results  are  achieved  rapidly,  and  the  end  is  not 
postponed  or  approached  in  a  halting,  zigzag  manner,  but 
the  modification  is  in  appearance  definite,  precise,  reminding 
one  of  the  regular  and  precise  operations  seen  in  chemical 
and  physical  processes. 

There  is  an  interesting  analogy  between  the  processes 
which  may  be  carried  on  in  organisms  in  modifying  the 
symmetries  by  combining  definite  characters,  and  those 
which  may  be  carried  on  in  crystallography,  as  for  example, 
where  certain  impurities  may  be  introduced  into  the  crystal- 
lized form  and  may  definitely  alter  the  attributes  of  the 
crystal,  such  as  shape,  color,  hardness,  specific  gravity, 
etc.  That  the  parallel  is  an  exact  one  there  is  no  evidence, 
but  it  is  at  least  suggestive  in  that  both  the  results  occur 
with  sharp  alternativeness  which  is  so  characteristic  of 
chemical  and  physical  operations. 

It  does  not  seem  probable  that  germinal  modifications 
in  form  and  symmetry  arise  through  the  changes  in  particu- 
lar chemical  constituents  within  the  germ  cell,  as,  for 
example,  a  particular  katalytic  agent,  or  the  rearrangement 
of  the  side  chains  in  some  complex  molecule,  because,  as  far 


258  Heredity  and  Eugenics 

as  is  known,  these  are  superficial  relations  and  are  not  of 
themselves  concerned  in  establishing  the  fundamental 
symmetries  and  activities  which  seem  to  be  in  the  main 
conditioned  and  controlled  by  the  colloidal  matrix  which 
underlies  all  visible  structure.  The  only  safe  statement  which 
can  be  made  at  present  is  an  acknowledgment  of  our  ignor- 
ance of  what  the  changes  are  in  the  germ  cell  which  are 
productive  of  new  arrangements  in  form  and  symmetry. 
However,  it  is  experimentally  proven  these  fundamental 
relations  can  be  altered  by  one  process  or  another,  thus 
giving  methods  of  inducing  changes  and  of  discovering 
what  changes  are  possible,  both  as  regards  the  limits  of 
change,  direction,  rate,  etc.,  and  this  knowledge  may  be 
of  great  practical  value  even  though  the  underlying  physico- 
chemical  operations  are  still  undetermined  and  possibly 
unknowable. 

In  the  modification  of  characteristics  which  are  directly 
conditioned  by  chemical  activities,  as,  for  example,  color, 
there  seems  a  greater  possibility  of  attaining  at  least  a 
general  idea  of  the  processes  involved  in  the  germ  cells  in 
producing  permanent  changes.  Pigments,  throughout  the 
organic  world,  are  pretty  generally  the  result  of  metabolic 
processes  and  are  probably  in  most  instances  the  result  of 
the  oxidation  of  various  cleavage  products  which  have 
themselves  been  formed  by  the  breaking  down  of  more  com- 
plex substances  within  the  cell.  Many  of  these  chromogen 
substances  are  possibly  waste  materials  in  the  organism, 
which  perhaps  could  not  be  further  utilized  in  the  economy 
of  the  animal,  so  this  method  arose  of  converting  them  into 
more  or  less  harmless  substances  and  depositing  them  in 
places  where  they  would  be  least  inconvenient  to  the 
organism.  This  old  conception  of  the  character  of  coloration 


Modification  of  Germinal  Constitution  of  Organisms       259 

meets  with  little  favor  today,  because  there  is  too  much 
good  evidence  to  show  that  even  under  adverse  conditions 
the  development  of  pigment  takes  place,  where  the  organism 
expends  in  developing  the  pigment,  material,  and  energy 
which  it  needs  to  carry  on  activities  vital  to  its  existence. 
The  pigment  substances  which  develop  in  connection  with 
pathological  growths  and  the  development  of  pigment  even 
in  the  face  of  starvation  are  all  indicative  of  the  deep-seated 
nature  of  pigment  formation  in  organisms. 

The  capacity  to  produce  a  given  pigment  is  as  firmly 
a  part  of  the  germinal  constitution  as  are  structural  char- 
acters, which,  by  some  at  least,  are  regarded  as  the  only 
attributes  worth  considering.  It  is  well  known  that  in  all 
organisms  there  is  in  nearly  all  cells  at  least  the  possibility 
of  producing  from  the  ordinary  breaking  down  of  the  sub- 
stance of  the  cell,  materials  which  can  serve  as  the  chromogen 
base  for  the  elaboration  of  various  kinds  of  pigment,  but 
this  aspect  of  the  subject  has  been  considered  in  an  earlier 
part  of  this  paper. 

The  question  in  the  production  of  germinal  modifications 
of  the  pigment-forming  capacity  in  organisms  is,  what  is 
it  in  the  germ  cell  that  is  modified?  There  is  little  to 
warrant  an  assumption  that  these  phenomena  are  based  upon 
representative  particles  or  upon  individualized  entities  of 
any  sort,  and  I  doubt  if  many  investigators  really  attribute 
to  pangenes  and  biophores  the  capacity  and  importance 
which  some  writers  who  are  antagonists  to  the  method  of 
expression  seem  called  upon  to  believe. 

Perhaps  the  best  evidence  in  this  direction  is  that 
derived  from  the  studies  in  inheritance  by  the  Mendelians. 
Their  treatment  of  the  subject  of  color  inheritance  has 
shown  clearly  that  there  is  something  in  alternative  char- 


260  Heredity  and  Eugenics 

acters  which,  when  a  definite  array  of  conditions  are  brought 
together,  produce  a  definite  color,  and  when  another  array 
is  brought  together  a  different  color  results,  or  perhaps 
no  color. 

At  the  present  time  there  is  no  evidence  that  in  the  cells 
there  is  incapacity  for  the  production  of  pigment,  or  inca- 
pacity for  the  production  of  either  chromogen  or  enzyme. 
The  only  evidence  is  that  the  pigment  does  or  does  not 
appear  when  germ  cells  derived  from  parents  of  a  certain 
character  are  combined.  In  the  minds  of  some  it  follows 
from  this  that  something  is  lacking  in  the  way  of  a  specific 
activity;  hi  the  minds  of  others  it  is  due  to  the  fact  that  a 
sufficient  quantity  of  one  or  the  other  of  two  necessary 
substances  is  not  present.  Still  another  explanation  is 
that  there  is  lacking  strength  or  energy  to  produce  the  one 
or  the  other. 

Further,  the  situation  can  be  explained  by  adopting  the 
idea  of  inhibitors,  activators,  etc.,  which  would  inhibit  the 
appearance  of  pigment  in  one  case,  and  then,  by  the  inhibi- 
tion of  the  inhibitor  permit  the  appearance  of  pigment  in 
another  case.  Much  fine  evidence  exists  from  the  work 
of  the  neo-Mendelian  hybridologists  that  factors,  deter- 
miners, accelerators,  and  inhibitors  exist  and  can  be  sub- 
jected to  experimental  tests;  however,  to  attempt  to 
explain  observed  conditions  by  asserting  that  the  organism 
is  incapable  of  producing  the  requisite  amount  of  chromogen 
or  activator  is  really  no  explanation,  because  it  is  well  known 
that  a  minimum  amount  of  activator  may  convert  an  almost 
unlimited  amount  of  chromogen  into  a  color-forming  sub- 
stance, provided  the  substance  produced  as  a  result  of  the 
katalyzing  process  is  removed  with  sufficient  rapidity  so  as 
not  to  impede  the  process.  This  is  a  well-known  principle 


Modification  of  Germinal  Constitution  of  Organisms      261 

in  all  katalytic  action.  It  does  not  seem  a  plausible  expla- 
nation of  germinal  color  variation  to  attempt  to  place  it 
upon  a  quantitative  basis,  in  view  of  the  well-known  facts 
of  katalysis.  Likewise,  explanation  of  the  situation  as  being 
due  to  varying  germinal  strength,  energy  units,  energy,  etc., 
does  not  aid,  and  only  confuses  a  situation  already  suffi- 
ciently confusing.  If  by  strength  is  meant  strength  of 
katalyzer,  there  again  a  weak  agent  may  produce  a  relatively 
large  result  if  advantageously  placed  and  given  a  sufficiently 
long  time  in  which  to  act  to  bring  about  a  definite  result,  and 
a  relatively  weak  agent  may,  under  advantageous  condi- 
tions, convert  a  relatively  enormous  amount  of  chromogen 
into  pigment-forming  substance.  It  would  be  of  interest  to 
know  the  chemical  constitution  of  some  of  the  attributes; 
hi  the  case  of  albino  animals,  for  example,  is  the  chromogen 
present,  and  is  the  oxidizing  agent  absent  or  vice  versa? 
It  seems  improbable  that  the  oxidizing  enzymes  should  be 
entirely  lacking,  and  it  may  be  true  that  there  is  a  specificity 
in  these  enzymes,  as  has  been  suggested  by  various  authors, 
and  a  specific  enzyme  might  well  be  absent,  and  in  its 
absence  there  would  be  no  production  of  color. 

As  far  as  I  am  able  to  get  at  the  processes  involved  hi 
the  production  of  color  variations  by  means  of  incident 
physical  and  chemical  factors,  it  seems  that  the  change  is 
one  which  involves  the  entire  mechanism  of  the  cell,  and 
is  not  resident  in  any  particular  part  thereof.  By  experi- 
mental means  I  have  produced  a  modified  condition  of 
coloration,  and  in  this  the  interactions  of  chromogen  and 
katalyzer  are  conditioned  in  their  appearance  and  inter- 
action during  ontogeny  by  the  mass  in  which  they  are,  and 
are  entirely  dependent  upon  the  capacity  of  the  mass  to 
retard,  accelerate,  or  extend  the  rate  and  time  of  action, 


262  Heredity  and  Eugenics 

or  to  remove  the  by-products  which  would  inhibit  the 
katalyzing  action  which  would  normally  go  on.  Under 
the  modified  conditions  there  may  be  produced  no  greater 
alteration  in  the  germ  than  a  reversed  action  of  some 
enzyme,  and  although  the  same  enzyme  may  be  present, 
its  reversed  action  is  such  that  the  pigment-forming  sub- 
stance is  not  formed,  but  its  activity  is  directed  to  other 
activities  than  to  building  pigment-forming  substances. 
The  same  enzyme  may  again  be  reversed  in  its  direction 
either  by  combining  with  some  other  substance,  or  by  being 
acted  upon  by  some  incident  force,  and  this  reversal  of  action 
in  the  enzyme  may  therefore  produce  the  formation  of 
color  substances.  It  does  not  of  necessity  follow  that  the 
changes  induced  are  at  all  concerned  with  the  substances 
which  actually  themselves  form  the  pigment.  For  example, 
in  germinal,  modifications  which  have  been  produced,  where 
the  color  is  diminished  in  intensity,  there  may  be  identical 
amounts  of  chromogen  and  enzyme,  but  the  changes  may  be 
due  to  changes  in  other  factors  which  are  necessary  to  the 
color  formation  by  removing  from  the  field  of  operation 
certain  inhibiting  by-products. 

It  is  possible  that  a  profitable  point  of  attack  upon  these 
problems  lies  in  this  direction.  The  chief  difficulty,  however, 
is  the  small  size  of  most  germ  cells,  and  in  those  of  large 
size  the  existence  in  the  egg  of  a  large  amount  of  stored 
food  supply  effectually  inhibits  investigation.  It  is  prob- 
able that  for  the  present,  interpretation  of  the  process  of 
germinal  change  must  be  more  by  analogy  than  by  actual 
physical  and  chemical  analysis. 

In  the  experimental  production  of  modifications  of  the 
germ  plasm  two  definite  ideas  as  to  the  nature  of  the  change 
have  been  expressed.  MacDougal  is  of  the  opinion  that 


Modification  of  Germinal  Constitution  of  Organisms       263 

in  many  of  his  derivatives  all  of  the  attributes  of  the  organ- 
ism were  modified  each  more  or  less  independently  of  the 
others.  I  have  expressed  the  opinion  that,  as  far  as  my 
observations  go,  one  character  is  in  the  main  most  modified, 
and  then  a  greater  or  less  array  of  lesser  characters  are  less 
modified  in  correlation.  There  is  at  once  a  fundamental 
difference  between  these  two  expressions  of  experience,  a 
difference  which  may  be  due  to  the  difference  between  plants 
and  animals,  but  I  do  not  understand  how  all  the  attributes 
of  an  organism  can  be  modified  at  one  time  by  incident  forces. 
MacDougal  says,  "The  induced  forms  in  plants  show  many 
new  qualities  of  fairly  equal  importance  as  far  as  such  things 
may  be  estimated,  and  these  might  be  independent  of  each 
other." 

I  do  not,  at  least  in  animals,  feel  competent  to  determine 
the  equality  of  characters,  and  thus  far  I  have  never  seen 
examples,  where  any  considerable  array  of  characters  were 
modified  equally.  As  a  matter  of  fact,  I  have  no  basis 
in  experience  which  would  enable  me  to  decide  whether 
characters  were  modified  equally  or  not. 

If  one  accepts  a  particulate  conception  of  the  constitu- 
tion of  an  organism  as  a  true  expression  of  organic  con- 
stitution, the  modifiability  of  characters  as  expressed  by 
MacDougal  would  be  the  natural  result.  I  have  thus  far 
seen  no  evidence  of  such  a  condition,  at  least  in  the  materials 
under  my  observation,  and  I  am  therefore  compelled  to 
regard  the  organism  as  a  whole  in  the  sense  that  it  represents 
a  state  of  stability  which  is  achieved  and  retained  by  a 
mass  of  matter  under  a  given  set  of  conditions.  The  com- 
bined elements  are  not  independent  and  do  not  exist  in  the 
organism  as  individualities,  but  as  component  parts  of  the 
whole,  as  long  as  they  comprise  a  part  of  that  particular 


264  Heredity  and  Eugenics 

substance,  even  though  they  are  capable  of  unlimited  meta- 
thetic  change  in  heredity. 

There  is  another  point  upon  which  MacDougal  and  I 
differ.  MacDougal  says,  that  "his  new  plants  do  not 
hybridize  freely,  if  at  all,  even  when  grown  with  branches 
interlocking  with  the  parental  type,"  which  differs  from  the 
conditions  which  I  have  found,  where  intercrossing  occurs 
freely  with  the  parent  species.  Comparison  is  difficult 
between  organisms  so  widely  separated  as  those  used  by 
MacDougal  and  myself,  and  it  is  entirely  possible  that  the 
results  of  particular  processes  may  result  differently  in 
different  organisms. 

The  results  obtained  by  Gager  through  the  use  of  radium 
upon  different  plants,  the  modifications  of  Sempervivum  by 
Klebs,  the  changes  in  yeasts  and  bacteria,  etc.,  can  hardly 
be  incorporated  at  the  present  time  in  this  discussion  in 
that  they  have  not  been  carried  far  enough.  Gager 's 
opinion  that  the  inheritable  results  obtained  by  him  were 
possibly  due  to  a  disturbance  in  the  chromosome  complex, 
is  simply  an  explanation  based  upon  an  old  morphological 
conception.  It  has  not  yet  been  shown  that  specific  chromo- 
somes are  endowed  with  specific  characters  resident  in 
them,  and  until  that  point  is  decided  definitely  the  explana- 
tion of  germinal  variations  on  the  basis  of  chromosome 
behavior  must  stand  aside. 

In  animals  the  experiments  of  Kammerer,  Pshibram, 
Woltereck,  Morgan,  and  the  older  experiments  of  Fischer, 
Standfuss,  Weismann,  and  others,  do  not  furnish  data  for 
a  discussion  of  and  far  less  for  a  solution  of  the  problem. 
However,  an  important  point  is  established  by  all  of  these 
investigations  which  show  uniformly  that  the  germ  cells  are 
most  susceptible  to  the  influences  that  produce  germinal 


Modification  of  Germinal  Constitution  of  Organisms       265 

changes  immediately  before  and  during  maturation.  This 
period  is  known  to  be  a  critical  one  in  the  life  of  the  germ  cell, 
and  is  a  time  when  many  processes  are  in  progress,  and  when 
there  exists  a  delicate  balance  susceptible  of  being  per- 
manently upset.  There  is  evidence  hi  some  of  my  experi- 
ments to  show  that  earlier  periods  in  the  life-history  of  the 
egg  are  susceptible  to  stimuli  and  produce  at  these  earlier 
periods  more  profound  modifications  than  are  produced 
later,  but  are  more  difficult  to  induce.  During  the  growth 
period  there  is  a  constantly  increasing  elaboration  of  poten- 
tialities, with  an  increasing  array  of  substances  and  sym- 
metries, and  a  slight  change  in  this  primary  constitution 
might  result  in  large  end  results. 

It  is  evident  that  the  problem  of  germinal  change  is  one 
of  difficulty,  and  involves  more  of  indirect  than  of  direct 
methods  of  investigation.  There  is  little  reason  to  expect 
that  present  biochemical  methods  can  give  a  solution,  but 
they  may  give  valuable  suggestions  for  further  indirect 
investigation.  It  seems  not  improbable,  however,  that 
this  problem,  like  so  many  others  in  biology,  must  await  the 
solution  of  the  larger  question  of  what  life  is  before  it  will 
be  possible  to  express  in  exact  terms  the  nature  of  germinal 
changes.  Our  present  status,  with  several  methods  of  pro- 
duction and  much  knowledge  of  the  behavior  of  induced 
germinal  changes  available,  is  a  basis  from  which  great 
advances  in  knowledge  and  in  operation  may  reasonably  be 
expected. 


CHARLES  BENEDICT  DAVENPORT 

Station  of  Experimental  Evolution,  Carnegie  Institution  of 
Washington 


CHAPTER  VIII 

THE  INHERITANCE  OF  PHYSICAL  AND  MENTAL  TRAITS 
OF  MAN  AND  THEIR  APPLICATION  TO  EUGENICS 

The  general  laws  of  heredity  have  already  been  fully 
explained.  But  every  person  has  a  different  way  of  express- 
ing them  and  a  little  repetition  will  do  no  harm;  and  so, 
very  briefly,  I  will  recapitulate  the. principles  of  heredity. 

First  of  all,  we  find  useful  the  principle  of  the  unit- 
character.  Whether  it  be  ultimately  accepted  or  discarded, 
it  is  useful  today,  and  so  we  accept  it  as  a  guiding  hypothesis. 
According  to  this  principle  characters  are,  for  the  most  part, 
inherited  independently  of  each  other,  and  each  trait  is 
inherited  as  a  unit  or  may  be  broken  up  into  characters 
that  are  so  inherited. 

Next  it  must  be  recognized  that  characters,  as  such,  are 
not  inherited.  Strictly,  my  son  has  not  my  nose,  because 
I  still  have  it;  what  was  transmitted  was  something  that 
determined  the  shape  of  his  nose,  and  that  is  called  in 
brief  a  "determiner. "  So  the  second  principle  is  that  unit- 
characters  are  inherited  through  determiners  hi  the  germ 
cells. 

And  finally,  it  is  recognized  that  there  really  is  no  inherit- 
ance from  parent  to  child,  but  that  parent  and  child 
resemble  each  other  because  they  are  derived  from  the 
same  germ  plasm,  they  are  chips  from  the  same  old  block; 
and  the  son  is  the  half-brother  to  his  father,  by  another 
mother. 

These  three  principles  are  the  three  cornerstones  of 
heredity  as  we  know  it  today,  the  principles  of  the  inde- 

269 


270  Heredity  and  Eugenics 

pendent  unit-characters  each  derived  from  a  determiner 
in  the  germ  plasm. 

It  is  my  agreeable  task  to  show  in  how  far  the  known 
facts  of  heredity  in  man  are  in  accord  with  these  principles. 
I  may  say  at  the  outset  that  I  have  no  doubt  that  all  human 
traits  are  inherited  in  accordance  with  these  principles; 
but  knowledge  proceeds  slowly  in  this  field. 

As  a  first  illustration  I  may  take  the  case  of  human  eye 
color.  The  iris  is  made  up  of  a  trestle  work  of  fibers,  in 
which  are  suspended  particles  that  give  the  blue  color. 
In  addition,  in  many  eyes,  much  brown  pigment  is  formed 
which  may  be  small  in  amount  and  gathered  around  the 
pupil,  or  so  extensive  as  to  suffuse  the  entire  iris  and  make 
it  all  brown.  It  is  seen,  then,  that  the  brown  iris  is  formed 
by  something  additional  to  the  blue.  And  brown  iris  may 
be  spoken  of  as  a  positive  character,  depending  on  a  deter- 
miner for  brown  pigment;  and  blue  as  a  negative  character, 
depending  on  the  absence  of  the  determiner  for  brown. 

Now  when  both  parents  have  brown  eyes  and  come 
from  an  ancestry  with  brown  eyes,  it  is  probable  that  all 
of  their  germ  cells  contain  the  determiner  for  brown  iris 
pigmentation.  So  when  these  germ  cells,  both  carrying 
the  determiner,  unite,  all  of  the  progeny  will  receive  the 
determiner  from  both  sides  of  the  house;  consequently  the 
determiners  are  double  in  their  bodies  and  the  resulting  iris 
pigmentation  may  be  said  to  be  duplex.  When  a  character 
is  duplex  in  an  individual  that  means  that  when  the  germ 
cells  ripen  in  the  body  of  that  individual  each  contains  a 
determiner.  So  that  individual  is  capable,  so  far  as  he  is  con- 
cerned, of  transmitting  his  trait  in  undiminished  intensity. 

If  a  parent  has  pure  blue  eyes,  that  is  evidence  that  in 
neither  of  the  united  germ  cells  from  which  he  arose  was 


Inheritance  of  Physical  and  Mental  Traits  271 

there  a  determiner  for  iris  pigmentation;  consequently  in 
respect  to  brown  iris  pigmentation  such  a  person  may  be 
said  to  be  nulliplex.  If  now  such  a  person  marry  an  indi- 
vidual duplex  in  eye  color,  in  whom  all  of  the  germ  cells 
contain  the  determiner,  each  child  will  receive  the  deter- 
miner for  iris  pigmentation  from  one  side  of  the  house  only. 
This  determiner  will,  of  course,  induce  pigmentation,  but 
the  pigmentation  is  simplex,  being  induced  by  one  deter- 
miner only.  Consequently,  the  pigmentation  is  apt  to  be 
weak.  When  a  person  whose  pigment  determiners  have 
come  from  one  side  of  the  house  forms  germ  cells,  half 
will  have  and  half  will  lack  the  determiner.  If  such  a 
person  marry  a  consort  all  of  whose  germ  cells  contain  the 
determiner  for  iris  pigmentation,  all  of  the  children  will,  of 
course,  receive  the  iris  pigmentation,  but  in  half  it  will  be 
duplex  and  in  the  other  half  it  will  be  simplex.  If  the  two 
parents  both  be  simplex,  so  that,  in  each,  half  of  the  germ 
cells  possess  and  half  lack  the  determiner  in  the  union  of 
germ  cells,  there  are  four  events  that  are  equally  apt  to 
occur:  (i)  an  egg  with  the  determiner  unites  with  a  sperm 
with  the  determiner;  (2)  an  egg  with  the  determiner  unites 
with  a  sperm  without  the  determiner;  (3)  an  egg  without 
the  determiner  unites  a  sperm  with  the  determiner;  (4)  an 
egg  without  the  determiner  unites  with  a  sperm  without  the 
determiner.  Thus  the  character  is  duplex  in  one  case, 
simplex  in  two  cases,  and  nulliplex  in  one  case;  that  is,  one 
in  four  will  have  no  brown  pigment,  or  will  be  blue  eyed. 
If  one  parent  be  simplex,  so  that  the  germ  cells  are  equally 
with  and  without  the  determiner,  while  the  other  be  nulli- 
plex, then  half  of  the  children  will  be  simplex  and  half 
nulliplex  in  eye  pigment.  Finally,  if  both  parents  be  nulli- 
plex in  eye  pigmentation  (that  is,  blue  eyed),  then  none  of 


272  Heredity  and  Eugenics 

their  germ  cells  will  have  the  determiner,  and  all  children 
will  be  nulliplex,  or  blue  eyed.  I  have  gone  into  the  inherit- 
ance of  eye  color  at  some  length  because  it  serves  as  a 
paradigm  of  the  method  of  inheritance  of  any  unit-character. 

Let  us  now  consider  some  of  the  physical  traits  of  man 
that  follow  the  same  law  as  brown  eye  color,  traits  that  are 
clearly  positive,  and  due  to  a  definite  determiner  in  the 
germ  plasm.  And  first,  I  may  refer  to  hair  color. 

Hair  color  is  due  either  to  a  golden-brown  pigment  that 
looks  black  in  masses,  or  else  to  a  red  pigment.  The 
lighter  tints  differ  from  the  darker  by  the  absence  of  some 
pigment  granules.  If  neither  parent  has  the  capacity  of 
producing  a  large  quantity  of  pigment  granules  in  the  hair, 
the  children  cannot  have  that  capacity,  that  is,  two  flaxen- 
haired  parents  have  only  flaxen-haired  children.  But  a 
dark-haired  parent  may  be  either  simplex  or  duplex;  and 
so  two  such  parents  may  produce  children  with  light  hair; 
but  not  more  than  one  out  of  four.  In  general,  the  hair 
color  of  the  children  tends  not  to  be  darker  than  that  of 
the  darker  parent.  Skin  pigment  follows  a  similar  rule. 
It  is  really  one  of  the  surprises  of  modern  studies  that 
skin  pigment  should  be  found  to  follow  the  ordinary  law 
of  heredity;  it  was  commonly  thought  to  blend.  In 
crosses  between  Negroes  and  Caucasians,  such  a  blend  was 
stated  to  occur,  and  it  was  believed  to  be  permanent,  so 
long  as  the  hybrids  were  mated  together.  Actually,  the 
method  of  inheritance  is  like  that  of  hair  pigment,  the 
skin  color  of  the  children  rarely  much  exceeds  that  of  the 
darker  parent.  There  are  stories  of  two  white  parents 
having  black-skinned  children,  and  if  these  are  true  they 
constitute  striking  exceptions  to  the  general  rule.  The 
inheritance  of  skin  color  is  not  dependent  on  race;  two 


Inheritance  of  Physical  and  Mental  Traits  273 

blondes  never  have  brunette  offspring,  but  brunettes  may 
have  blondes.  The  extreme  case  is  that  of  albinos  with  no 
pigment  in  skin,  hair,  and  iris.  Two  albinos  have  only  albino 
children,  but  albinos  may  come  from  two  pigmented  parents. 
Similarly,  straight-haired  parents  lack  curliness,  and 
two  such  have  only  straight-haired  children.  Also  two 
tall  parents  have  only  tall  children.  Shortness  is  the  trait: 
tallness  is  a  negative  character.  Also  when  both  parents 
lack  stoutness  (are  slender),  all  children  tend  to  lack  it. 


0 


N]  [N]  BjO        03        LJlO 


B  m    o  1 


FIG.  80.  —  Inheritance  of  monilithrix  —  a  positive  character.  Black  symbols 
represent  affected  individuals.  —  ANDERSON. 

We  may  now  consider  briefly  the  inheritance  of  certain 
pathological  or  abnormal  states,  to  see  in  how  far  the  fore- 
going principles  hold  for  them  also.  We  shall  find  that 
sometimes  the  abnormal  condition  is  positive,  due  to  a  new 
trait;  but  sometimes,  on  the  contrary,  the  normal  condi- 
tion is  the  positive  one  and  the  trait  is  due  to  a  defect. 

Among  conditions  due  to  a  new  determiner  may  be  men- 
tioned a  beaded  peculiarity  in  the  form  of  the  hair,  called 
monilithrix.  Affected  persons  tend  to  have  affected  off- 
spring (Fig.  80).  Two  unaffected  parents  do  not  ordinarily 


274  Heredity  and  Eugenics 

have  affected  children  (in  the  illustrative  case  nothing  is 
known  about  one  of  the  two  parents).  When  one  parent 
only  is  affected  about  half  of  the  children  are  affected,  since 
each  affected  person  is  simplex. 

Again,  some  family  strains  exhibit  imperfection  of  hair 
or  even  baldness  associated  with  imperfect  nails  (Fig.  81). 
Here  there  seems  to  be  a  determiner  that  stops  the  develop- 
ment of  these  organs  of  the  skin.  Normal  persons  are  with- 
out this  determiner  and  so  cannot  have  affected  children. 


norm,     norm 


FIG.  81. — Pedigree  of  a  family  with  poorly  nourished  nails  and  hair  (black 
symbols). — Nicoixfi  ET  HAUPR£. 

Still  another  peculiarity  of  the  skin  is  due  to  a  positive 
character.  This  is  a  thickening  of  the  palms  of  the  hands 
and  soles  of  the  feet  (Fig.  82).  Here  all,  or  half,  of  the 
children  of  an  affected  parent  are  affected,  but  normals  of 
the  strain,  who  marry  outside  of  the  family,  will  have  no 
thick-skinned  children. 

In  some  persons  the  color  of  the  hair  of  the  head  is  not 
uniform,  but  there  are  patches  of  white  hair  in  the  midst 


Inheritance  of  Physical  and  Mental  Traits 


275 


of  a  prevailing  brown  head  of  hair.  This  spotted  condition 
is  due  to  a  positive  factor,  just  like  spottedness  in  mice. 
From  a  spotted  parent  at  least  half  the  offspring  are  spotted; 


FIG.  82. — Pedigree  of  a  family  with  tyloses  (T).    Note  that    11  affected  per- 
sons have  at  least  one  parent  affected. — UNNA. 


r 


OrB  BrO  ®rD  B,O  BiO  *  6rD 

I   I  3N  I   r   i 


FIG.  83.  —  Pedigree  of  faulty  enamel  of  teeth.  This  peculiarity  appears  only 
in  the  offspring  of  an  affected  parent,  consequently  it  is  a  positive  trait.  —  TURNER. 

but  a  person  with  uniform  coat  belonging  to  the  spotted 
strain  will  have  no  children  with  the  white  patch. 

Probably  the  same  law  is  followed  in  the  case  of  families 
without  teeth  and  also  in  families  with  faulty  enamel  of  the 
teeth  (Fig.  83).  Apparently  there  is  a  determiner  that 


276  Heredity  and  Eugenics 

partially  or  fully  prevents  the  development  of  the  tooth 
germ. 

Some  peculiarities  of  the  eye  are  clearly  inherited. 
Thus  the  condition  in  which  the  lens  of  the  eye  becomes 
clouded  and  opaque  seems  to  be  due  to  a  positive  determiner, 
and  this  is  most  clearly  seen  when  cataract  appears  in 
middle  life.  For,  all  cases  of  presenile  cataract  appear  in  the 
offspring  of  affected  persons,  and  two  unaffected  persons 
probably  never  have  descendants  with  cataract  (Fig.  84). 


•  6®^« 


FIG.  84. — Pedigree  of  a  family  with  presenile  cataract  (black  symbols). 
Numbers  in  circles  indicate  unaffected  individuals.  Cataract  in  offspring  of 
affected  parents  only. 

The  same  law  holds  for  a  peculiarity  of  the  eye  such  that 
the  affected  person  cannot  see  by  weak  light,  such  as  the 
light  of  lamp,  electric  lights,  etc.  (night  blindness).  There 
is  clearly  a  positive  determiner,  since  affected  persons  have 
affected  offspring,  but  if  the  parents  are  not  affected  (thus 
proving  the  absence  of  the  determiner  from  their  germ 
plasm),  the  offspring  are  never  affected.  These  con- 
clusions are  based  on  the  remarkable  pedigree  compiled 
by  Nettleship,  involving  over  two  thousand  individuals. 


Inheritance  of  Physical  and  Mental  Traits 


277 


Many  peculiarities  of  the  skeleton  are  clearly  due  to  a 
positive  determiner  that  inhibits  the  normal  development. 
Thus  the  case  is  cited  of  a  father  with  a  deformed  clavicle 
or  collar  bone;  of  his  seven  children,  five  have  the  clavicles 
of  a  more  or  less  abnormal  form.  Likewise  in  polydactyl- 
ism,  or  extra-fingeredness,  there  is  some  positive  factor 
that  induces  the  formation  of  the  extra  toe;  but  normal- 
toed  persons  of  a  polydactyl  strain,  being  without  the 
determiner,  will  have  all  children  with  five  toes  only. 

The  same  is  true  of  brachydactyly.  There  is  something 
that  stops  the  growing  of  the  fingers  to  the  normal  length, 


ION 


4N  [N]   (D)          6N    |D]  (N)  (D)  «N    5N   JN 
FIG.  85. — Pedigree  of  a  family  with  diabetes  insipidus.    D,  affected  persons 

so  that  if  the  determiner  gets  into  the  zygote  from  either 
side  of  the  house,  the  child  will  be  short-fingered,  but  not 
otherwise. 

Diabetes  is  a  common  disease  which  seems  to  belong 
to  this  category  (Fig.  85).  Here  again  two  normal  parents 
may  have  defective  children  but  only  when  the  defect  occurs 
in  the  germ  plasm  of  both  sides  of  the  house. 

The  applications  of  these  facts  regarding  abnormalities 
and  diseases  that  are  of  a  positive  sort  have  an  importance 
for  eugenics.  They  are  all  characterized  by  this,  that  they 
usually  appear  in  each  generation  and  do  not  skip  genera- 


278  Heredity  and  Eugenics 

tions.  They  are  relatively  common  in  any  given  family, 
since  half  or  all  of  an  affected  fraternity  commonly  show 
the  trait.  If  the  trait  is  an  undesirable  one  and  it  must  not 
be  reproduced,  then  the  eugenical  advice  is  for  an  affected 
person  to  abstain  from  having  children.  But  an  unaffected 
person  belonging  to  this  strain  may  marry  an  unaffected  per- 
son with  impunity,  and  it  is  immaterial  for  the  inheritance 
of  this  trait  whether  they  be  cousins  or  not. 

We  have  next  to  consider  the  class  of  abnormalities  and 
weaknesses  that  are  due  to  the  absence  of  a  determiner,  to 
the  disappearance  of  a  trait  that  tends  to  normality.  A 
good  example  of  such  a  defect  is  seen  in  albinism,  already 
referred  to  (Fig.  86).  In  this  large  pedigree  the  number  of 
affected  individuals  is  small,  and  they  are  frequently  derived 
from  two  pigmented  persons;  cousin  marriages  are  common. 
The  defect  may  be  carried  in  the  germ  cells  of  two  normal 
parents;  hence  its  appearance  from  such  parents. 

Another  example  is  seen  in  Thomsen's  disease,  a  disease 
that  is  characterized  by  a  slow  initial  contraction  of  a 
muscle  after  stimulus  (Fig.  86).  Here  again  two  normal 
consorts  have  some  affected  children  and  cousin  marriages 
are  common. 

There  is  reason  for  asserting  that  weakness  of  the  mucous 
membranes  is  due  to  a  similar  defect  (Fig.  88).  If  both 
parents  are  without  the  determiner  for  resistance,  then  of 
course  all  offspring  will  be  non-resistant.  When  one 
parent  is  liable  to  colds  and  pneumonia  and  the  other  has 
catarrh,  the  children  suffer  from  tonsilitis,  diphtheria,  and 
inflammations  of  the  throat  and  lungs.  But  if  one  parent 
be  non-resistant,  and  the  other,  though  resistant,  have 
some  non-resistant  germ  cells,  at  least  half  of  the  offspring 
will  be  non-resistant. 


Inheritance  of  Physical  and  Mental  Traits 


279 


280 


Heredity  and  Eugenics 


FIG.  87.— Pedigree  of  Thorn- 
sen's  disease  (black  symbols) .  Ap- 
pears in  cousin  marriages  even 
from  affected  parents;  hence  due  to 
a  defect.  Squares  indicate  males; 
circles,  females. — BERNHARDT. 


Some  eye  diseases  are  clearly  due  to  a  defect  in  the 
determiner.  Such  is  the  case  with  an  inflammatory  con- 
dition of  the  retina  in  which  pigment  is  deposited  and  the 

patient  ultimately  loses  his  sight 
(Fig.  89).  This  disease  fre- 
quently appears  in  the  children 
of  two  normal  persons  who  are 
cousins,  and  consequently  both 
carry  the  defect  in  their  germ 
cells. 

Deaf-mutism  also  is  due  to  a 
defect;  but  the  nature  of  the 
defect  is  different  in  different 
cases.  Deaf -mutism  is  so  varied 
that  frequently  two  unrelated 
deaf  mutes  may  have  hearing 
children  (Fig.  90).  But  if  the  deaf-mute  parents  be 
cousins,  the  chances  that  the 
deafness  is  due  to  the  same 
unit  defect  are  increased  and 
all  of  the  children  will  probably 
be  deaf. 

We  come  now  to  consider 
mental  peculiarities,  and  here 
at  once  enter  a  vast  field  in 
which  surprising  discoveries 
have  been  made  in  recent  years, 
and  which  point  to  the  cause  of 
many  of  our  social  difficulties  and  the  way  out. 

First,  consider  the  facts  of  feeble-mindedness.  This 
term  is  a  lumber-room  and  comprises  various  mental  defi- 
ciencies, such  as  inability  to  count,  to  repeat  phrases,  to 


n 


pntvm.      t/fp/Sf   fhfoat  rrjptr  fauttfu  foftjt/ifrs 
/onjf/'f'*  /rot/^f  Srou6/e 

FIG.  88. — Pedigree  showing 
inheritance  of  a  tendency  toward 
colds,  catarrh,  and  respiratory 
diseases. 


Inheritance  of  Physical  and  Mental  Traits  281 

learn  to  write  or  to  draw,  to  meet  difficult  situations  by 
intelligent  adjustment,  to  control  the  appetites  and  passions, 
to  appreciate  moral 
ideas.  Many  persons 

who  are  not  regarded  -  I      I 

as  feeble-minded  have       n  Q&  JPJ9  0  Q  Q 

some  of  these  or  simi-          , — , — HL,      J_^ — — 
lar  defects;  the  typi-      =•  •  C  1   •  •  •  • 

Cally  feeble-minded  'FKJ  Sg.-Pedigree  of  reLifo  pigmentosa 

are  defective  in  Several      (black    symbols)    in    a    family    described    by 

or  many  such  mental     Mooren.-NETTLEsmP. 

traits.     In  what  follows  I  shall  use  feeble-mindedness  in 

the  latter  sense. 

From  the  studies  of  £r.  Goddard  and  others,  it  appears 
that  when  both  parents  are  f  eeble-minded  all  of  the  children 
will  be  so  likewise;  this  conclusion  has  been  tested  again  and 
again  (Fig.  91).  But  if  one  of  the  parents  be  normal  and  of 


D 


n       I"3 I  j     JL f  , .  J^f  . .    . — .      JL  c  JL.7     I  a       l» 

i   N    N     N    (D)T| |  (D)T[DJ  ln]T(£)TLnJ  D    D 

/Vfc    drof-mvf't'n  tn  I  I  ^* ^  I 

t*./drrn  <>/•  yr*ntl- 

Cf,:/^f  I 

V  D  0T©'  0T^        N*  0T®^     ©'  ©'  ©°  0 


Y  is?  N?  N 

FIG.  90. — Pedigree  of  a  family  with  deaf  mutes  (D)  in  a  large  proportion  of  the 
later  generations. 

normal  ancestry,  all  of  the  children  may  be  normal  (Fig. 
92);    whereas,  if  the  normal  person  have  defective  germ 


282 


Heredity  and  Eugenics 


cells,  half  of  his  progeny  by  a  feeble-minded  woman  will  be 
defective. 

Epilepsy  and  feeble-mindedness  may  replace  each  other 
(as  equivalents)  in  pedigrees.    This  is  well  illustrated  by 


FIG.  91. — Pedigree  of  a  family  with  a  high  proportion  of  feeble-minded  per- 
sons (F).    Squares,  males;  circles,  females;  d.  inf.,  died  in  infancy. — GODDARD. 


FIG.  92. — Pedigree  of  a  family  in  which  the  feeble-minded  grandmother 
married  twice;  by  a  normal  husband  she  had  normal  children;  but  by  an  alco- 
holic, sex-offending  (Sx),  doubtless  feeble-minded  husband  she  had  only  feeble- 
minded children. — GODDARD. 

the  figure  (Fig.  93)  in  which  a  feeble-minded  sex  offender 
has  by  an  epileptic  daughter  two  feeble-minded  children 
and  one  epileptic  child. 

Many  criminals,  especially  those  who  offend  against  the 
person,  are  feeble-minded,  as  is  shown  by  the  way  they 


Inheritance  of  Physical  and  Mental  Traits 


283 


occur  in  fraternities  with  feeble-mindedness,  or  have  feeble- 
minded parents  (Fig.  94).  The  test  of  the  mental  condition 
of  relatives  is  one  that  may  well  be 
applied  by  judges  in  deciding  upon 
the  responsibility  of  an  aggressor.  It 
is  to  be  hoped  that  the  conservatism 
of  the  law  upon  this  matter  may  be 
speedily  overcome. 

Not  only  the  condition  of  imper- 
fect mental  development,  but  also 
that  of  inability  to  withstand  stress 
upon  the  nervous  system,  may  be 
inherited.  From  the  studies  of  Dr. 
Rosanoff  and  his  collaborators,  it  ap- 
pears that  if  both  parents  be  subject 
to  manic  depressive  insanity  or  to 
dementia  precox,  all  children  will  be 
neuropathic  also  (Fig.  95);  that  if 
one  parent  be  affected  and  come  from  a  weak  strain,  half 


t/>W 

anenctph. 

FIG.  93. — The  pedigree 
of  a  family  in  whose  second 
generation  incest  produces 
an  epileptic  daughter,  but 
by  whose  own  father  she 
has  one  epileptic  and  two 
feeble-minded  children;  A, 
alcoholic;  C,  criminalistic; 
E,  epileptic;  F,  feeble- 
minded; Sx,  licentious. 


H  ui  (3)  if&  ©rD  LJ-O  O-D  DTOEJjO 


T 

fJO    afteny*  ffO    fjf  </raf 

t*l>      foffoof 


d  Op  Dr6-D  6-D 

b6-n6 


FIG.  94. — Pedigree  of  a  feeble-minded  family  in  which  criminalistic  (C)  and 
licentious  (Sx)  traits  also  appear. 


284  Heredity  and  Eugenics 

of  the  children  are  liable  to  go  insane;  and  that  nervous 
breakdowns  of  these  types  never  occur  if  both  parents  be 
of  sound  stock. 

Even  the  condition  of  general  nervousness  is  an  indica- 
tion of  a  nervous  weakness  that  is,  apparently,  due  to  the 
absence  of  a  determiner.  Thus  when  a  person  belonging  to 
a  neurotic  strain  marries  a  normal  person  whose  father 
died  of  apoplexy,  some  neurotic  and  feeble-minded  children 
may  appear  in  the  offspring. 

Finally,  a  study  of  families  with  special  abilities  reveals 
a  method  of  inheritance  quite  like  that  of  nervous  defect. 


©  EJ  ©  (N)  [N]  (N)  [N]f  (N)  [N]  ®  Q  QN]  (N)  Q  0  [N] 


FIG.  95. — Pedigree  of  a  family  in  which  the  father's  parents  (upper  left)  are 
both  nervous  (N)  and  have  four  nervous  children.  The  mother  is  nervous;  so  were 
her  father  and  four  of  her  brothers  and  sisters,  while  one  is  insane.  Of  the  three 
grandchildren  one  is  insane  (I),  one  epileptic  (E),  and  one  extremely  nervous  (N). — 
CANNON  AND  ROSANOFF. 

If  both  parents  be  color  artists,  or  have  a  high  grade  of 
vocal  ability  or  are  litterateurs  of  high  grade,  then  all  of 
their  children  tend  to  be  of  high  grade  also.  If  one  parent 
has  high  ability,  while  the  other  has  low  ability  but  has 
ancestry  with  high  ability,  part  of  the  children  will  have 
high  ability  and  part  low.  It  seems  like  an  extraordinary 
conclusion  that  high  ability  is  inherited  as  though  due  to 
the  absence  of  a  determiner  in  the  same  way  as  feeble- 
mindedness and  insanity  are  inherited.  We  are  reminded 
of  the  poet:  "Great  wits  to  madness  sure  are  near  allied." 
Evidence  for  the  relationship  is  given  by  pedigrees  of  men 


Inheritance  of  Physical  and  Mental  Traits  285 

of  genius  that  often  show  the  combination  of  ability  and 
insanity  (Fig.  96).  May  it  not  be  that  just  that  lack  of 
control  that  permits  "flights  of  the  imagination"  is  related 
to  the  flightiness  characteristic  of  those  with  mental  weak- 
ness or  defect  ? 

These  studies  of  inheritance  of  mental  defect  inevitably 
raise  the  question  how  to  eliminate  the  mentally  defective. 
This  is  a  matter  of  great  importance  because,  on  the  one 
hand,  it  is  now  coming  to  be  recognized  that  mental  defect 


T     T       r 

I  Aoaf 

I  alej/aa 

I        _  uS 

no  6  dniiO 


d  do 


ddddd  o  C-n  dO  d-o  c 

n>nv  fxrrff^a,  A./  •//  orfnt  mrtvJ 

•tr      atofitf  ita/drr  /urr  mrr/,<,n  a*./,',,  afrAfy  \ 

'  *  ff  ' 


j 

-Aon    innnfirr  6oot  n>nv  fxrrff^a,  A./  •//  orfnt  mrtvJ 

fy  \ 

' 


d 

FIG.  96. — Pedigree  of  a  family  with  great  inventive  and  artistic  ability,  in 
whose  earlier  generations  appear  insanity  (I),  suicidal  tendency,  and  eccentricity. 

is  at  the  bottom  of  most  of  our  social  problems.  Extreme 
alcoholism  is  usually  a  consequence  of  a  mental  make-up 
in  which  self-control  of  the  appetite  for  liquor  is  lacking. 
Pauperism  is  a  consequence  of  mental  defects  that  make 
the  pauper  incapable  of  holding  his  own  in  the  world's 
competition.  Sex  immorality  in  either  sex  is  commonly 
due  to  a  certain  inability  to  appreciate  consequences,  to 
visualize  the  inevitableness  of  cause  and  effect,  combined 
sometimes  with  a  sex-hyperaesthesia  and  lack  of  self-control. 


286  Heredity  and  Eugenics 

Criminality  in  its  worst  forms  is  similarly  due  to  a  lack  of 
appreciation  of  or  receptivity  to  moral  ideas. 

If  we  seek  to  know  what  is  the  origin  of  these  defects, 
we  must  admit  that  it  is  very  ancient.  They  are  probably 
derived  from  our  apelike  ancestors  in  which  they  were 
normal  traits.  There  occurs  in  man  a  strain  that  has  not 
yet  acquired  those  traits  of  inhibition  that  characterized 
the  more  highly  developed  civilized  persons.  The  evidence 
for  this  is  that,  as  far  back  as  we  go,  we  still  trace  back  the 
black  thread  of  defective  heredity. 

We  have  now  to  answer  the  question  as  to  the  eugenical 
application  of  the  laws  of  inheritance  of  defects.  First, 
it  may  be  pointed  out  that  traits  due  to  the  absence  of  a 
determiner  are  characterized  by  their  usual  sparseness  in 
the  pedigree,  especially  when  the  parents  are  normal;  by 
the  fact  that  they  frequently  appear  where  cousin  marriages 
abound,  because  cousins  tend  to  carry  the  same  defects 
in  their  germ  plasm  though  normal  themselves;  by  the 
fact  that  two  affected  parents  have  exclusively  normal 
children,  while  two  normal  parents  who  belong  to  the  same 
strain,  or  who  both  belong  to  strains  containing  the  same 
defect,  have  some  (about  25  per  cent)  defective  children. 
But  a  defective  married  to  a  pure  normal  will  have  no 
defective  offspring. 

The  clear  eugenical  rule  is  then  this:  Let  abnormals 
marry  normals  without  trace  of  the  defect,  and  let  their 
normal  offspring  marry  in  turn  into  strong  strains;  thus 
the  defect  may  never  appear  again.  Normals  from  the 
defective  strain  may  marry  normals  of  normal  ancestry; 
but  must  particularly  avoid  consanguineous  marriages. 

The  sociological  conclusion  is:  Prevent  the  feeble- 
minded, drunkards,  paupers,  sex-offenders,  and  criminalistic 
from  marrying  their  like  or  cousins  or  any  person  belonging 


Inheritance  of  Physical  and  Mental  Traits  287 

to  a  neuropathic  strain.  Practically  it  might  be  well  to 
segregate  such  persons  during  the  reproductive  period  for 
one  generation.  Then  the  crop  of  defectives  will  be  reduced 
to  practically  nothing. 

I  cannot  close  without  referring  to  a  remarkable  method 
of  inheritance  of  human  traits,  namely,  the  sex  limited. 
As  everyone  knows,  there  are  certain  traits,  such  as  facial 
hair,  which  are  associated  with  one  sex;  and  a  tendency 
to  heavy  growth  of  beard  may  be  transmitted  by  a  mother's 
germ  cells  to  her  son.  In  this  case  the  determiner  for  heavy 
beard  does  not  develop  JCTTL, 

in  the  female,  but  only  (S/rQD  0 

in  the  male,  under  the  |_ 

stimulus,   as  it  were, 
of  the  testicular  se- 
cretions; or  perhaps    c  " 
in  the  absence  of  an              *    *        «***«  <*    * 
inhibiting   enzyme                        **^  °f  famUy  with  c°lor' 
secreted  by  the  ovary. 

But  in  another  class  of  cases  the  inheritance  is  most 
complex.  Thus  usually  only  males  are  color-blind,  but 
they  do  not  transmit  their  condition  to  their  sons.  On 
the  other  hand,  the  normal  women  of  this  strain  will  have 
color-blind  sons  (Fig.  97). 

This  has  been  a  great  mystery,  but  thanks  to  the  recent 
studies  in  sex  chromosomes  by  Wilson,  Morgan,  and  others, 
it  is  a  mystery  no  longer.  It  is  explained  by  one  fact  and 
one  hypothesis.  The  fact  is  that  the  male  has  only  one 
sex  chromosome,  while  the  female  has  two.  The  hypothesis 
is  that  a  factor  for  distinguishing  colors  is  lacking  in  the 
affected  male  and  is  lost  out  of  the  single  sex  chromosome 
of  such  a  male.  Now  the  consequence  of  these  two  prin- 
ciples can  be  seen  easily.  Let  the  striated  disk  (S,  Fig.  98) 


288  Heredity  and  Eugenics 

stand  for  the  single  male  sex  chromosome,  which,  by  hypothe- 
sis, lacks  the  color  distinguishing  factor.  Let  the  white 
disk  (W)  symbolize  the  absence  of  a  chromosome  in  a  germ 
cell.  Let  the  black  disks  (B)  represent  the  two  female 
sex  chromosomes  with  the  factor  of  color-sight.  Then  the 
union  of  S-\-B  gives  the  female  sex  and  has  the  determiner 
for  color,  albeit  simplex.  The  union  W-\-B  gives  the  male 
sex  and  also  has  the  determiner  for  color-sight.  Hence 
.*  neither  sons  nor  daughters  of  a  color- 

*  blind  man  are  color-blind.     If  the  son 

5      K^i  4^  ,  . 

V  B      marry  a  normal  woman,  it  is  clear 

w  Q  ^  that  (since  no  S  comes  into  the  union) 

the  children  are  normal.    But  if  the 

FIG.  98.-Diagram  illus-       daughters    marry     half   Qf    the    males 

tratmg  method  of  inherit-  °  •'  ' 

ing  sex-limited  characters,     will  receive  the  single  S  chromosome 

The  circles   represent    sex      ancj   g^   will  fog   color-blind.      Thus 

chromosomes.  ,11  f  i     •   i  A  •>  P 

the  long  famous  knight  s  move  form 

of  heredity  of  color-blindness  is  explained.  Several  other 
traits  are  inherited  in  the  same  way:  bleeding,  imperfect 
development  of  the  iris,  and  atrophy  of  the  optic  nerve. 
In  all  these  cases  unaffected  males  may  marry  with  impun- 
ity; but  females  of  the  strain  who  have  affected  brothers 
should  not  have  children. 

The  foregoing  considerations  bring  clearly  to  mind  the 
great  advance  that  has  been  made  hi  recent  years  in  the 
analysis  of  the  inheritance  of  traits.  At  last  it  is  possible 
to  give  definite  advice  to  those  about  to  marry,  or  who  do 
not  wish  to  transmit  their  undesirable  traits.  Of  the 
method  of  inheritance  of  many  traits  we  are  still  in  ignor- 
ance. In  the  absence  of  detailed  knowledge,  the  best  gen- 
eral advice  that  can  be  given  is  this;  marry  dissimilars. 
Weakness  in  any  trait  should  marry  strength  in  that  trait; 
and  strength  may  marry  weakness. 


RELATIONS   OF   BARRIERS   TO   HUMAN  BREEDING 

In  the  period  before  our  Civil  War,  while  men  were 
looking  for  an  excuse  if  not  a  justification  for  slavery  the 
subject  of  the  unity  of  man's  species  was  much  discussed. 
In  these  later  days,  removed  from  the  passions  of  politics, 
as  a  purely  academic  question  the  inquiry  has  been  reopened. 
Ideas  have  changed  much  in  the  intervening  fifty  or  sixty 
years  and  now  we  have  to  define  all  over  again  what  is 
meant  by  species  or  race. 

In  connection  with  the  new  ideas  of  heredity  we  have 
gained  a  new  conception  of  species  and  race.  We  now 
apply  the  terms  indifferently  and  say  a  species,  or  race,  is 
an  intergenerating  group  of  individuals  distinguished  by 
the  possession  of  one  or  more  unit-characters.  As  we  look 
over  mankind  we  note  at  once  the  groups  that  have  always 
been  distinguished :  the  Negroes  with  black  skin  and  woolly 
hair;  the  oriental  race  with  olive  or  yellow  skin  and  (typi- 
cally) narrow  eyes;  the  American  Indian  with  brown-red 
skin  and  long  straight  hair,  and  the  Caucasians  with  white 
skin  and  high  cephalic  index.  This  naive  classification 
may  have  sufficed  for  the  dawn  of  anthropology,  but  today 
we  recognize  its  insufficiency.  In  the  group  of  Caucasians 
are  hundreds  of  distinctive  characters  upon  each  of  which 
a  race  might  be  founded.  There  are  the  brunette  skin  and 

1  Much  of  the  present  chapter  is  reprinted  from  the  author's  book,  Heredity 
in  Relation  to  Eugenics,  and  it  appears  here  through  the  courtesy  of  the  publishers 
of  that  book,  Messrs.  Henry  Holt  &  Co. 

289 


290  Heredity  and  Eugenics 

the  blonde;  the  straight  hair  and  the  curly;  the  flaxen 
hair  and  the  brown  and  the  red;  the  blue  eyes  and  the  dark; 
the  straight  nose,  the  aquiline,  and  the  pug;  the  broad 
head  and  the  high  and  the  narrow;  the  thin  lips  and  the 
thick,  and  so  through  the  categories.  The  only  reason  why 
we  do  not  have  distinct  species  of  men  distinguished  by 
such  traits  is  because  of  the  extensive  hybridization  that 
man  is  undergoing.  Everywhere,  brown  eyes  mate  with 
blue,  black  hair  with  flaxen,  curly  with  straight,  and  so  on. 
Man's  potential  races  are  not  realized  just  because  of  the 
universal  interfertility  of  the  different  races  and  because 
of  the  mobility  of  man's  habitat. 

Now  is  there  any  evidence  aside  from  a-priori  consid- 
erations for  testing  this  view  ?  Are  the  potentialities  that 
we  assume  anywhere  realized?  Is  the  theory  of  man's 
universal  hybridization  more  than  a  figment  of  the  imagi- 
nation ? 

First,  let  us  admit  that  evidence  for  the  unity  of,  say, 
the  Caucasian  race  has  been  offered  by  the  biometricians. 
They  have  said  if  the  race  is  homogeneous  it  will  show  itself 
by  the  biometric  test.  Measure  a  trait  in  10,000  individ- 
uals; and  plot  the  relative  frequency  of  the  different  values 
found.  If  that  frequency  rises  in  a  gentle  curve  from  its 
lowest  value  to  a  maximum  at  some  middle  value  and  then 
falls  again  smoothly  to  the  highest  value  the  curve  is  a 
simple  curve  and  this  has  been  regarded  as  proving  a  unit- 
population.  But  it  does  not  prove  it;  for  we  now  realize 
that  even  the  apparently  simple  curve  may  be  the  result- 
ant of  many  more  elementary  curves  whose  number  dimin- 
ishes uniformly  on  both  sides  of  the  center.  The  elementary 
curves  are  the  ones  that  include  the  fluctuations  of  the  real 
units. 


Geography  of  Man  in  Relation  to  Eugenics  291 

Second,  the  real  units  may  be  isolated  by  the  simple 
process  of  preventing  the  random  hybridization  and  ensuing 
breeding  within  the  type.  This  result  has  been  nearly 
realized  in  small  oceanic  islands,  and  in  other  isolated 
communities.  It  will  be  interesting  to  look  at  some  of 
these  isolated  places  and  learn  what  has  been  produced  in 
them. 

At  Swans'  Island,  Maine,  much  consanguinity  in  mar- 
riage occurs;  cousin  marriages  are  the  rule.  A  consequence 
has  been  that  the  defect  of  feeble-mindedness  is  unusually 
common  and,  were  the  process  to  continue  for  many  more 
generations,  a  race  with  this  trait,  among  others,  would 
doubtless  become  established. 

At  Western  Martha's  Vineyard  a  careful  genealogical 
study  has  been  made  by  Dr.  Alexander  Graham  Bell  and 
much  consanguineous  marriage  has  been  found.  Here  is, 
or  was,  being  formed  a  deaf-mute  colony;  one  out  of  every 
twenty-five  was  already  a  deaf  mute. 

At  Block  Island,  with  a  population  of  fifteen  hundred, 
much  consanguineous  marriage  has  occurred,  and  a  non- 
fecund  strain  has  been  isolated.  On  the  Banks  off  Palmico 
Sound  consanguineous  marriage  occurs  with  extraordinary 
frequency;  and  a  strain  characterized  by  suspicion,  insan- 
ity, and  mental  dulness  is  being  formed.  At  George  Island 
near  Eleuthera  Island,  one  of  the  Bahamas,  long  inbreed- 
ing has  produced  a  race  that  tends  toward  dwarf  stature 
and  eye  defects,  including  cataracts. 

What  is  true  of  islands  holds  for  other  isolated  situations. 
A  physician  at  an  extreme  point  of  the  peninsula  of  Dor- 
chester County,  Maryland,  writes  that  marriages  there  are 
usually  consanguineous  and  a  race  of  dwarfs  and  cripples 
is  being  formed.  Mountain  valleys  of  the  Ramapo,  Cats- 


2g  2  Heredity  and  Eugenics 

kill,  Taconic,  and  Adirondack  masses  show  many  endoga- 
mous  centers.  In  one  place  a  race  of  criminals  is  being 
formed;  in  another  a  feeble-minded  strain;  in  another  an 
albino  race,  and  so  on.  There  is  reason  for  thinking  that 
the  valleys  of  eastern  Kentucky  and  Tennessee  are  centers 
of  inbreeding  and  nearly  pure  races  are  being  formed  there. 
In  larger  settled  countries  the  process  has  gone  farther. 
From  the  Chin  Hills,  Burmah,  one  hears:  "Rau  Vau  Village 
has  been  isolated  for  about  seven  generations.  It  contains 
about  sixty  houses  and  possibly  two  hundred  inhabitants. 
Of  these  ten  are  idiots,  many  are  dwarfs,  and  some  hydro- 
cephalic.  A  number  of  cases  of  syndactylism  or  webbing 
of  hands,  and  brachydactyly  occur." 

Only  slightly  less  important  than  the  geographical  barriers 
are  the  social.  A  public  institution  brings  together  men  and 
women  so  intimately  that  marriages  frequently  occur  after 
leaving  the  institution.  Thus  two  persons  with  the  same 
trait  become  parents.  Almshouses  in  which  segregation  of 
the  sexes  is  imperfect  yield  numerous  depauperate  and 
imbecile  offspring,  and  there  is  reason  for  suspecting  that 
sanatoria  and  some  hospitals  for  the  "curable"  insane 
lead  to  marriage  of  two  weak  persons.  That  institutions 
for  the  deaf  lead  to  the  marriage  of  similarly  defective 
is  notorious.  Thus  Dr.  Bell,  who  has  long  warned  us  of 
the  imminent  danger  of  the  formation  of  a  deaf  variety 
of  the  human  race  in  America,  says:  "I  desire  to  direct 
attention  to  the  fact  that,  in  this  country  deaf  mutes  marry 
deaf  mutes.  An  examination  of  the  records  of  some  of  our 
institutions  for  the  deaf  and  dumb  reveals  the  fact  that 
such  marriages  are  not  the  exception  but  the  rule." 

The  barrier  of  language  is  extremely  important  hi  pro- 
moting consanguineous  marriages,  or  the  matings  of  persons 


Geography  of  Man  in  Relation  to  Eugenics  293 

with  the  same  defect.  Thus  with  regard  to  deaf  mutes, 
Bell  says:  "The  practice  of  the  sign  language  hinders  the 
acquisition  of  the  English  language;  it  makes  deaf  mutes 
associate  together  in  adult  life,  and  avoid  the  society  of 
hearing  people;  it  thus  causes  the  intermarriage  of  deaf 
mutes  and  the  propagation  of  their  physical  defect."  The 
importance  of  this  barrier  is  seen  among  recent  immigrants. 
These  tend  to  herd  together,  largely  because  of  a  desire  to  be 
with  people  who  speak  the  same  language.  Thus  immigration, 
instead  of  directly  tending  to  promote  matings  of  dissimilar 
and  unrelated  blood,  has,  at  first,  an  exactly  opposite  effect. 

The  barrier  of  race  is  of  the  very  greatest  importance  hi 
promoting  marriages  of  kin — especially  if  one  race  be  in  a 
marked  minority,  as  the  Negroes  are  in  New  Hampshire 
and  the  whites  are  in  the  Mississippi  River  bottom,  around 
Vicksburg,  or  in  parts  of  the  West  Indies. 

Finally  the  barrier  of  religious  sect  has  been  erected 
again  and  again  to  insure  the  intermarriage  of  the  faithful 
only.  This  is  illustrated  by  the  teachings  of  the  Society 
of  Friends  and  smaller  sects,  such  as  the  Dunkers,  Shakers, 
and  Amish.  Of  the  Dunkers  it  is  written:  "In  their  early 
history  marriage  out  of  the  church  was  punishable  by 
expulsion.1  It  is  still  frowned  upon  but  the  process  of 
liberalization  now  in  progress  had  modified  the  attitude  of 
the  church.  In  some  congregations  families  intermarry 
generation  after  generation.  But  the  degree  of  kinship  is 
not  so  close  that  any  evil  results  appear  in  the  offspring." 
Nevertheless  one  sees  the  danger  that  any  small  sect 
with  such  tenets  runs.  A  critical  study  of  the  Amish  of 
Pennsylvania  with  much  marriage  of  kin  shows  a  sufficient 
progeny  of  epilepsy  and  crippled  children  to  serve  as  a 

1Chronicon  Ephratense,  96,  246. 


294  Heredity  and  Eugenics 

warning  that  a  defect  is  in  the  blood  of  some  of  the  strains 
that  in  time  will  affect  the  entire  sect  who  remain  in  that 
part  of  the  country. 

MIGRATIONS  AND  THEIR  EUGENIC   SIGNIFICANCE 

The  human  species  has  come  to  occupy  the  entire 
habitable  globe.  This  fact  is  mute  testimony  of  man's 
migratory  capacity  and  tendencies.  Just  as  the  Norwegian 
lemming  has  been  observed,  in  consequence  of  several 
years  of  favorable  conditions  for  breeding  in  its  mountain 
home,  to  spread  over  the  surrounding  territory  in  great 
bands,  seeking  less  crowded  breeding  grounds;  even  as  the 
army  worm  and  the  grasshopper  swarm  from  their  native 
territory;  so  man,  also,  under  the  pressure  of  crowded 
conditions,  poverty,  and  oppression,  or  lured  by  brightei 
prospects  elsewhere,  may  move  in  hordes  to  other  lands 
that  seem  to  offer  better  opportunities.  Thus  Asia  seems 
to  have  debouched  her  surplus  population  upon  Europe 
in  the  shape  of  the  Huns  during  the  fourth  and  fifth  cen- 
turies of  our  era  and  the  Turks  during  the  fourteenth  and 
fifteenth  centuries.  So  the  Anglo-Saxons  and  the  Normans 
successively  swarmed  upon  England.  So,  among  savages, 
the  Masai  of  Africa  moved  upon  the  neighboring  tribes  and 
established  themselves  over  much  of  southeastern  Africa. 
So  in  the  last  three  centuries  the  Americas  and  Australia 
have  witnessed  the  greatest  migrations  that  the  world  has 
ever  seen,  hundreds  of  thousands  annually  coming  from 
overcrowded  Europe,  and  Asia  to  the  "New  World." 

For  us  in  America  the  phenomena  of  migration  should 
have  a  special  interest.  Excepting  for  the  few  scores  of 
thousands  of  Indians  there  was  a  continent  devoid  of  a 
population — a  clean  slate  upon  which  history  was  to  be 


Geography  of  Man  in  Relation  to  Eugenics  295 

written  and  where  the  effect  of  "blood"  in  determining 
that  history  might  be  traced. 

Since  the  first  few  scores  of  thousands  of  immigrants 
had  the  greatest  influence  on  the  ideals  of  the  colonies  they 
established  and  since  their  blood  has  had  the  longer  time 
to  show  its  effect,  and  since  their  traits  have  had  the  great- 
est chance  to  disseminate  widely,  they  deserve  special 
consideration. 

On  the  James  River  the  first  settlers  consisted  chiefly 
of  "discredited  idlers  and  would-be  adventurers,"  more 
than  half  of  them  "gentlemen"  of  good  family  but  untrained 
hi  labor,  trusting  for  a  change  of  fortune  in  the  new  land. 
Even  later,  men,  women,  and  children  were  sent  by  the 
London  Company  to  colonize  the  new  land  and  that  com- 
pany was  not  particular  as  to  quality.  Even  felons,  mur- 
derers, and  women  of  the  streets  were  at  times  sent  over 
from  London  to  relieve  the  city  of  them,  and  the  governor, 
who  was  a  pure  euthenist  and  seemed  to  think  the  better 
environment  would  cure  their  evil  ways,  welcomed  all. 

But  a  better  blood  soon  crowded  into  Virginia  to  redeem 
the  colony.  Upon  the  execution  of  Charles  I  (1649)  a  host 
of  royalist  refugees  sought  an  asylum  here,  and  the  immi- 
gration of  this  class  continued  even  after  the  Restoration. 
By  this  means  the  province  was  enriched  by  a  germ  plasm 
which  easily  developed  such  traits  as  good  manners,  high 
culture,  and  the  ability  to  lead  in  all  social  affairs — traits 
combined  in  remarkable  degree  in  the  "first  families  of 
Virginia."  From  this  complex  and  the  similar  complex 
of  Maryland  has  come  much  of  the  bad  blood  that  found 
the  retreats  of  the  mountain  valleys  toward  Kentucky  and 
Tennessee  to  its  liking  and  that  spread  later  into  Indiana 
and  Illinois  and  gave  rise,  in  all  probability,  to  the  Ishmael- 


296  Heredity  and  Eugenics 

ites,  a  family  of  which  hundreds  have  been  supported  in 
the  almshouses  and  jails  of  Indiana.  From  this  complex 
came  also  some  of  America's  greatest  statesmen  and  war- 
riors, the  Randolphs,  the  Marshalls,  the  Madisons,  the 
Curtises,  the  Lees,  the  Fitzhughs,  the  Washingtons,  and 
many  others  born  with  the  instinct  to  command.  Such 
are  the  descendants  of  the  high-spirited  cavaliers.  It  might 
have  been  predicted  that  the  future  state  would  be  "the 
Mother  of  Presidents,"  and  that  in  a  civil  war  the  severest 
battles  should  be  fought  on  her  soil. 

Farther  north,  at  Manhattan  Island,  a  settlement  was 
being  made  by  another  sort  of  people:  a  band  of  Dutch 
traders.  The  fur  trade  with  the  Indians  waxed  profitable. 
The  more  venturesome  established  trading-posts  up  the 
North  River,  even  as  far  as  the  present  site  of  Albany; 
others  went  east  as  far  as  the  Connecticut  River.  They 
maintained  friendly  relations  with  the  Indians,  as  the  main 
source  of  their  wealth,  and  under  their  protection  estab- 
lished trading-posts,  even  along  the  valley  of  the  Mohawk. 
Little  wonder  that  such  blood,  under  the  favorable  environ- 
ment of  an  admirable  location,  has  created  the  commercial 
center  of  the  western  world. 

On  the  bleak  coasts  of  New  England  were  being  founded 
settlements  of  idealists,  men  who  were  willing  to  undergo 
exile  for  conscience'  sake.  They  included  many  scholars 
like  the  pastor  Robinson;  Brewster  who,  while  self -exiled 
at  Leyden,  instructed  students  at  the  University;  John 
Winthrop,  "of  gentle  breeding  and  education";  John 
Davenport,  of  New  Haven,  whom  the  Indians  named 
"heap  study-man."  Little  wonder  that  the  germ  plasm 
of  these  colonies  of  men  of  deep  convictions  and  scholar- 
ship should  show  its  traits  in  the  great  network  of  its 


Geography  of  Man  in  Relation  to  Eugenics  297 

descendants  and  establish  New  England's  reputation  for 
conscientiousness  and  love  of  learning  and  culture.  As  it 
was  almost  the  first  business  of  the  founders  of  the  colonies 
of  Massachusetts  Bay  and  New  Haven  to  found  a  college, 
so  their  descendants — the  families  of  Edwards,  Whitney, 
Dwight,  Eliot,  Lowell,  Woolsey,  and  the  rest — have  not 
only  led  in  literature,  philosophy,  and  science,  but  have 
carried  the  lamps  of  learning  across  the  continent,  light- 
ing educational  beacons  from  Boston  to  San  Francisco. 
Nor  is  it  an  accident  that  on  the  soil  tilled  by  these  dis- 
senters from  the  Established  Church  of  England  should  be 
spilled  the  first  blood  of  the  American  Revolution. 

Later,  to  the  shores  of  the  Delaware,  Penn  led  his  band 
of  followers,  consisting  of  men  and  women  whose  natures 
were  attracted  to  his  principles  of  thrift,  absence  of  show, 
and  non-resistance.  The  germ  plasm  of  his  followers  soon 
peopled  Penn's  woods,  and  it  is  not  due  solely  to  chance 
that  Pennsylvania  has  the  largest  number  of  homes  owned 
by  their  occupants  and  free  from  debt  of  any  state. 

Thus  the  characteristics  of  each  commonwealth  were 
early  determined  by  the  traits  of  the  persons  who  were 
attracted  toward  them.  These  traits  still  persist  in  their 
dwindling  descendants  who  strive  to  secure  the  preservation 
in  the  state  of  the  ideals  inculcated  by  their  forefathers. 

One  common  characteristic  these  early  immigrants  had, 
which  led  them  to  leave  family  and  friends,  to  undergo  the 
trials  of  the  long  sea  voyage  in  small  ships  and  to  settle  in 
a  rigorous  climate  among  unreliable  savages,  and  that  was  a 
willingness  to  break  with  tradition,  to  exchange  the  old  for 
the  new  and  better.  This  trait,  that  amounts  in  extreme 
cases  to  a  wanderlust,  is  illustrated  by  the  history  of  many 
a  pioneer.  For  example,  Simeon  Hoyt  landed  in  Salem, 


298  Heredity  and  Eugenics 

Mass.,  in  1628;  went  in  the  first  company  of  settlers  to 
Charleston  (1629);  went  to  Dorchester  (1630)  with  the  first 
company  of  settlers  there;  joined  the  church  at  Scituate 
(1635),  and  built  a  house  there;  then,  probably  in  the 
spring  of  1636,  migrated  to  Windsor,  Connecticut  Colony, 
which  he  helped  found.  In  1649  ne  was  granted  land  at 
Fairfield,  and  in  1657  he  died  at  Stamford.  Thus  in  the 
space  of  thirty  years  Simeon  Hoyt  lived  in  seven  villages 
in  America  and  was  a  founder  of  at  least  three  of  them— 
a  truly  restless  spirit,  like  many  another  settler,  and  the 
parent  of  a  restless  progeny! 

Still  another  example  is  that  of  Hans  Jorst  Heydt  of 
Strasburg.  He  fled  to  Holland  when  his  native  town  was 
seized  by  Louis  XIV,  married  there  Anna  Maria  DuBois, 
a  French  Huguenot  refugee  from  Wicres,  and  came  with 
her  to  America  and  settled  at  New  Paltz  on  the  Hudson 
about  1710.  Schismatic  dissensions  having  broken  out  in 
the  new  colony,  Heydt,  with  others,  left  and  settled,  about 
1717,  in  Philadelphia  County,  not  far  from  Germantown, 
where  he  acquired  several  hundred  acres  of  land,  estab- 
lished a  colony,  built  mills,  and  entered  upon  various  com- 
mercial enterprises  of  magnitude.  In  1731,  having  acquired 
a  grant  of  forty  thousand  acres  of  land  in  the  Shenandoah 
Valley,  he  migrated  thither,  became  known  as  Baron  Hite, 
and  died  there  in  1760.  One  of  his  friends,  Van  Metre, 
who  originally  settled  at  New  Paltz,  had  moved  first  to 
Somerset  County,  New  Jersey,  then  to  Salem  County  in 
the  same  colony;  later  to  Prince  George's  County,  Mary- 
land, and,  finally,  to  Orange  County,  Virginia.  These  are 
examples,  merely,  of  the  restlessness — often  enterprising 
restlessness — of  the  early  settlers,  and  it  persists  in  their 
descendants. 


Geography  of  Man  in  Relation  to  Eugenics  299 

Now  all  of  these  migrations  have  a  profound  eugenic 
significance.  The  most  active,  ambitious,  and  courageous 
blood  migrates.  It  migrated  to  America  and  has  made  her 
what  she  has  become;  in  America  another  selection  took 
place  hi  the  western  migrations,  and  what  this  best  blood 
— this  creme  de  la  crime — did  in  the  West  all  the  world 
knows.  Great  cities  like  Chicago,  with  its  motto  "I  will," 
arose  hi  a  generation  or  two  to  the  front  rank  of  world 
metropolises,  and  New  England,  the  early  home  of  the 
sewing  machine  and  the  cotton  gin,  has  yielded  the  palm 
to  the  Central  West,  the  home  of  the  reaping  machine  and 
the  aeroplane. 

And  when  the  best  and  strongest  migrated  the  weaker 
minds  were  left  behind  to  breed  hi  the  old  homestead.  A 
recent  report  of  the  British  "Committee  on  Physical 
Deterioration"  contains  the  testimony  of  Dr.  C.  R.  Browne 
about  conditions  in  the  west  of  Ireland.  He  says:  "The 
sound  and  the  healthy — the  young  men  and  young  women 
from  the  rural  districts  emigrate  to  America  in  tremendous 
numbers,  and  it  is  only  the  more  enterprising  and  the  more 
active  that  go,  as  a  rule."  And  Dr.  Kelly,  the  Roman 
Catholic  bishop  of  Ross  testified :  "  For  a  considerable  number 
of  years  it  has  been  only  the  strong  and  vigorous  that  go — 
the  old  people  and  the  weaklings  remain  behind  in  Ireland." 
And  even  hi  New  England  we  see  signs  of  decadence  of  the 
old  stock  and  men  speak  of  racial  deterioration.  But  the 
race  as  a  whole  has  not  deteriorated  but  only  the  New 
England  representatives — the  left-behinds  of  the  grand  old 
families,  whose  stronger  members  went  west. 

Likewise  in  the  rural  and  semi-rural  population  within 
a  hundred  miles  of  our  great  cities,  we  find  a  disproportion 
of  the  indolent,  the  alcoholic,  the  feeble-minded,  the  ne'er- 


300  Heredity  and  Eugenics 

do-well.  Thus  our  great  cities  lure  to  themselves  the  best 
of  the  rural  protoplasm  and  surround  it  with  conditions  that 
discourage  reproduction,  either  by  creating  a  disinclination 
to  marriage  or  making  it  inconvenient  and  expensive  to  have 
children.  So  our  great  cities  act  anti-eugenically,  sterilizing 
the  best  and  leaving  the  worst  to  reproduce  their  like. 

THE  INFLUENCE  OF  THE  SINGLE  GERM  PLASM  ON  THE  RACE 

As  one  stands  at  Ellis  Island  and  sees  pass  the  stream 
of  persons,  sometimes  five  thousand  in  a  day,  who  go 
through  that  portal  to  enter  the  United  States  and,  for  the 
most  part,  to  become  incorporated  into  it,  one  is  apt  to 
lose  sight  of  the  potential  importance  to  this  nation  of  the 
individual,  or,  more  strictly,  the  germ  plasm  that  he  or 
she  carries.  Yet  the  study  of  extensive  pedigrees  warns 
us  of  the  fact.  Every  one  of  those  peasants  will,  if  fecund, 
play  a  role  for  better  or  worse  in  the  future  history  of  this 
nation.  Formerly,  when  we  believed  that  traits  blend, 
a  characteristic  in  the  germ  plasm  of  a  single  individual 
among  thousands  seemed  not  worth  considering — it  would 
soon  be  lost  in  the  melting-pot.  But  now  we  know  that 
unit-characters  do  not  blend;  that  after  a  score  of  gener- 
ations the  given  characteristic  may  still  appear  unaffected 
by  the  repeated  union  with  foreign  germ  plasm.  So  the 
individual,  as  the  bearer  of  a  potentially  immortal  germ 
plasm  with  immutable  traits,  becomes  of  the  greatest 
interest.  A  few  examples  will  illustrate  this  law  and  its 
practical  importance. 

Elizabeth  Tuttle. — From  two  English  parents,  sire  at 
least  remotely  descended  from  royalty,  was  born  Elizabeth 
Tuttle.  She  developed  into  a  woman  of  great  beauty,  of 
tall  and  commanding  appearance,  striking  carriage,  "of 


Geography  of  Man  in  Relation  to  Eugenics  301 

strong  will,  extreme  intellectual  vigor.  On  November 
19,  1667,  she  married  Richard  Edwards  of  Hartford,  Con- 
necticut, a  lawyer  of  high  repute  and  great  erudition.  Like 
his  wife  he  was  very  tall,  and  as  they  both  walked  the 
Hartford  streets  their  appearance  invited  the  eyes  and 
admiration  of  all."  In  1691,  Mr.  Edwards  was  divorced 
from  his  wife.  After  his  divorce  Mr.  Edwards  remarried 
and  had  five  sons  and  a  daughter  by  Mary  Talcott,  a  medi- 
ocre woman,  average  in  talent  and  character  and  ordinary 
in  appearance.  None  of  Mary  Talcott's  progeny  rose 
above  mediocrity  and  the  descendants  gained  no  abiding 
reputation. 

Of  Elizabeth  Tuttle  and  Richard  Edwards  the  only  son 
was  Timothy  Edwards,  who  graduated  from  Harvard  College 
in  1691,  gaining  simultaneously  and  highly  exceptionally 
the  two  degrees  of  Bachelor  of  Arts  and  Master  of  Arts. 
He  was  pastor  of  the  church  in  East  Windsor,  Connecticut, 
for  fifty-nine  years.  Of  his  eleven  children  the  only  son 
was  Jonathan  Edwards,  one  of  the  world's  great  intellects, 
pre-eminent  as  a  divine  and  theologian,  president  of  Prince- 
ton College.  Of  the  descendants  of  Jonathan  Edwards 
much  has  been  written;  a  brief  catalogue  must  suffice: 
Jonathan  Edwards,  Jr.,  president  of  Union  College; 
Timothy  D wight,  president  of  Yale;  Sereno  Edwards 
Dwight,  president  of  Hamilton  College;  Theodore  D  wight 
Woolsey,  for  twenty-five  years  president  of  Yale  College; 
Jared  Sparks,  president  of  Harvard  College,  1849-53; 
Sarah,  wife  of  Tapping  Reeve,  founder  of  Litchfield  Law 
School,  herself  no  mean  lawyer;  Daniel  Tyler,  a  general  of 
the  Civil  War  and  founder  of  the  iron  industries  of  northern 
Alabama;  Ann  Maria,  wife  of  Edwards  Amasa  Park, 
president  of  Andover  Theological  Seminary,  herself  as 


302  Heredity  and  Eugenics 

astute  a  thinker  as  her  clerical  spouse;  Timothy  D wight  the 
second,  president  of  Yale  University  from  1886  to  1898; 
Theodore  William  Dwight,  founder  and  for  thirty-three 
years  warden  of  Columbia  Law  School;  Henrietta  Frances, 
wife  of  Eli  Whitney,  inventor  of  the  cotton  gin,  who,  burn- 
ing the  midnight  oil  by  the  side  of  her  ingenious  husband, 
helped  him  to  his  enduring  fame;  Merrill  Edward  Gates, 
president  of  Amherst  College;  Catherine  Maria  Sedgwick, 
of  graceful  pen;  Charles  Sedgwick  Minot,  authority  on 
biology  and  embryology  in  the  Harvard  Medical  School; 
Edith  Kermit  Carow,  wife  of  Theodore  Roosevelt,  and 
Winston  Churchill,  the  author  of  Coniston.  These  consti- 
tute a  glorious  galaxy  of  America's  great  educators,  students, 
and  moral  leaders  of  the  Republic. 

The  remarkable  qualities  of  Elizabeth  Tuttle  were  in 
the  germ  plasm  of  her  four  daughters  also:  Abigail  Stough- 
ton,  Elizabeth  Deming,  Ann  Richardson,  and  Mabel  Bige- 
low.  All  of  these  have  had  distinguished  descendants  of 
which  only  a  few  can  be  mentioned  here.  Robert  Treat 
Paine,  signer  of  the  Declaration  of  Independence,  was 
descended  from  Abigail;  the  Fairbanks  Brothers,  manu- 
facturers of  scales  and  hardware  at  St.  Johnsbury,  Ver- 
mont, and  the  Marchioness  of  Donegal  were  descended 
from  Elizabeth  Deming;  from  Mabel  Bigelow  came  Morri- 
son Waite,  chief  justice  of  the  United  States,  and  the  law 
author,  Melville  M.  Bigelow;  from  Ann  Richardson  pro- 
ceeded Marvin  Richardson  Vincent,  professor  of  Sacred 
Literature  at  Columbia  University  and  the  Marchioness  of 
Apesteguia,  of  Cuba.  Thus,  numerous  scholars,  inventors, 
and  publicists  trace  back  their  origin  to  the  germ  plasm  from 
which  (in  part)  Elizabeth  Tuttle  also  was  derived,  but  of 
which,  it  must  never  be  forgotten,  she  was  not  the  author. 


Geography  of  Man  in  Relation  to  Eugenics  303 

The  first  families  oj  Virginia. — This  remarkable  galaxy 
arose  by  the  intermarriage  of  representatives  of  various 
English  aristocratic  families.  The  story  of  these  early 
matings  is  briefly  as  follows :  Richard  Lee,  of  a  Shropshire 
family  that  held  much  land,  and  many  of  whose  members 
had  been  knighted,  went,  during  the  reign  of  Charles  I,  to 
the  colony  of  Virginia  as  secretary  and  one  of  the  king's 
Privy  Council.  "He  was  a  man  of  good  stature,  comely 
visage,  enterprising  genius,  sound  head,  vigorous  spirit, 
and  generous  nature."  He  gamed  large  grants  of  land 
in  Virginia.  His  son,  Richard,  married  in  1674,  Laetitia, 
daughter  of  Henry  Corbin  and  Alice  Eltonhead.  The 
Corbins  were  wealthy  and  extensive  landowners  in  England 
for  fourteen  generations,  and  the  Eltonheads  were  also  an 
aristocratic  family  and  extensive  landowners  of  Virginia, 
holding  high  offices  in  the  colony. 

Richard  and  Laetitia  Lee  had  six  sons  and  one  daughter, 
Ann.  Ann  married  Col.  William  Fitzhugh,  a  descendant 
of  the  English  barons,  military  men,  and  parliamentarians 
of  that  name.  Their  eldest  son  married  a  Carter,  and  one 
of  their  granddaughters  and  one  of  their  sons  married  a 
Randolph;  their- daughter,  Mary,  married  George  Washing- 
ton Parke  Custis,  and  became  the  grandmother  of  Robert 
E.  Lee.  Richard  Lee,  Jr.,  had  children  who  married  into  the 
families  of  Fairfax  and  Turberville.  A  brother  of  Richard, 
Thomas,  was  president  of  the  council  and  at  one  tune  acting 
governor  of  the  colony.  He  married  Hannah  Ludwell, 
descendant  of  a  brother  of  the  statesman,  Lord  Cottington; 
one  of  their  sons,  Richard  Henry  Lee,  prepared  at  the 
Continental  Congress  the  resolutions  for  independence; 
another,  Francis  Lightfoot  Lee,  was  a  member  of  Congress; 
and  still  another,  Thomas,  a  judge  of  the  General  Court. 


3°4  Heredity  and  Eugenics 

Another  son  of  Richard  and  Laetitia  Lee  was  Henry, 
who  married  Mary  Bland,  a  descendant  of  Sir  Thomas 
Bland,  and  a  granddaughter  of  Theodorick  Bland,  speaker 
of  the  House  of  Burgesses  and  member  of  the  Council. 
Their  three  sons  were  all  members  of  the  House  of  Bur- 
gesses and  some  were  in  the  House  of  Delegates,  in  con- 
ventions and  in  the  state  senate.  Such  was  the  product 
of  the  first  families  of  Virginia — statesmen,  military  men— 
the  necessary  product  of  their  germ  plasm. 

The  Kentucky  aristocracy. — Nearly  two  centuries  ago, 
John  Preston  of  Londonderry,  Irish  born  though  English 
bred,  married  the  Irish  girl,  Elizabeth  Patton,  of  Donegal, 
and  to  the  wilderness  of  Virginia  took  his  wife  and  built 
their  home,  Spring  Hill. 

Of  this  union  there  were  five  children:  Letitia,  who  married 
Colonel  Robert  Breckinridge;  Margaret,  who  married  Rev.  John 
Brown;  William,  whose  wife  was  Susannah  Smith;  Anne,  who  mar- 
ried Colonel  John  Smith;  and  Mary,  who  married  Benjamin  Howard. 
....  From  them  have  come  the  most  conspicuous  of  those  who  bear 
the  name  of  Preston,  Brown,  Smith,  Carrington,  Venable,  Payne, 
Wickliffe,  Wooley,  Breckinridge,  Benton,  Porter,  and  many  other 
names  written  high  in  history. 

They  were  generally  persons  of  great  talent  and  thoroughly  edu- 
cated; of  large  brain  and  magnificent  physique.  The  men  were 
brave  and  gallant,  the  women  accomplished  and  fascinating  and 
incomparably  beautiful.  There  was  no  aristocracy  in  America  that 
did  not  eagerly  open  its  veins  for  the  infusion  of  this  Irish  blood;  and 
the  families  of  Washington  and  Randolph,  and  Patrick  Henry,  and 
Henry  Clay,  and  the  Hamptons,  Wicklifles,  Marshalls,  Peytons, 
Cabells,  Crittendens,  and  Ingersolls  felt  proud  of  their  alliances  with 
this  noble  Irish  family. 

They  were  governors  and  senators  and  members  of  Congress,  and 
presidents  of  colleges  and  eminent  divines,  and  brave  generals  from 
Virginia,  Kentucky,  Louisiana,  Missouri,  California,  Ohio,  New  York, 
Indiana,  and  South  Carolina.  There  were  four  governors  of  old 


Geography  of  Man  in  Relation  to  Eugenics  305 

Virginia.  They  were  members  of  the  cabinets  of  Jefferson,  and 
Taylor,  and  Buchanan,  and  Lincoln.  They  had  major-generals  and 
brigadier-generals  by  the  dozen;  members  of  the  Senate  and  House 
of  Representatives  by  the  score;  and  gallant  officers  in  the  army  and 
navy  by  the  hundred.  They  furnished  three  of  the  recent  Demo- 
cratic candidates  for  Vice-President  of  the  United  States. 

The  quotation  has  a  scientific  value  in  comparison  with 
the  product  of  Elizabeth  Tuttle.  The  New  England  family 
glows  with  scholars  and  inventors;  the  Virginia  and  Ken- 
tucky families  with  statesmen  and  military  men.  The 
result  is  not  due  merely  to  the  difference  in  the  character- 
istics of  Elizabeth  Tuttle,  Richard  and  Laetitia  Lee,  John 
and  Elizabeth  Preston  respectively,  but  to  the  different 
traits  of  the  New  England  settlers  as  a  whole,  and  the  Vir- 
ginia cavalier-colonists  as  a  body.  The  initial  person 
becomes  a  great  progenitor  largely  because  of  some  fortu- 
nate circumstance  of  personal  gift  or  excellent  reputation 
that  enables  his  offspring  to  marry  into  the  "best  blood." 

The  Jukes. — On  the  other  hand,  we  have  the  striking 
cases  of  families  of  defectives  and  criminals  that  can  be 
traced  back  to  a  single  ancestor.  The  case  of  the  "Jukes" 
is  well  known.  We  are  first  introduced  to  a  man  known 
hi  literature  as  "Max,"  living  as  a  backwoodsman  in  New 
York  state,  and  a  descendant  of  the  early  Dutch  settlers; 
a  good-natured,  lazy  sot,  without  doubt  of  defective  mental- 
ity. He  has  two  sons  who  marry  two  of  six  sisters  whose 
ancestry  is  uncertain,  but  of  such  a  nature  as  to  lead  to 
the  suspicion  that  they  are  not  full  sisters.  One  of  these 
sisters  is  known  as  "Ada  Juke,"  also  as  "Margaret,  the 
mother  of  criminals."  She  was  indolent  and  a  harlot  before 
marriage.  Besides  an  illegitimate  son  she  had  four  legiti- 
mate children.  The  first,  a  son,  was  indolent,  licentious, 
and  syphilitic;  he  married  a  cousin  and  had  eight  children, 


306  Heredity  and  Eugenics 

all  syphilitic  from  birth.  Of  the  seven  daughters,  five  were 
harlots  and  of  the  others  one  was  an  idiot  and  one  of  good 
reputation.  Their  descendants  show  a  preponderance  of 
harlotry  in  the  females  and  much  consanguineous  marriage. 
The  second  son  was  a  farm  laborer,  was  industrious,  and 
saved  enough  to  buy  fourteen  acres  of  land.  He  married 
a  cousin  and  they  produced  three  still-born  children,  a 
harlot,  an  insane  daughter  who  committed  suicide;  an 
industrious  son,  who,  however,  was  licentious,  and  a  pauper 
son.  The  first  daughter  of  "Ada"  was  an  indolent  harlot 
who  later  married  a  lazy  mulatto  and  produced  nine  children, 
harlots  and  paupers,  who  produced  in  turn  a  licentious 
progeny. 

Ada  had  an  illegitimate  son  who  was  an  industrious  and 
honest  laborer  and  married  a  cousin.  Two  of  the  three 
sons  were  licentious  and  criminalistic  in  tendency,  and  the 
third  while  capable,  drank  and  received  outdoor  relief. 
All  of  the  three  daughters  were  harlots  or  prostitutes,  and 
two  married  criminals.  The  third  generation  shows  the 
eruption  of  criminality.  Excepting  the  children  of  the 
third  son,  none  of  whom  was  criminalistic,  we  find  among 
the  males  twelve  criminals,  one  licentious,  five  paupers, 
one  alcoholic,  and  one  unknown;  none  was  a  normal  citizen. 
Among  the  females,  eight  were  harlots,  one  a  pauper,  one 
a  vagrant,  and  two  unknown;  none  was  known  to  be 
reputable.  Thus  it  appears  that  criminality  lies  in  the 
illegitimate  line  from  Ada,  and  not  at  all  in  the  legitimate 
— doubtless  because  of  a  difference  in  germ  plasm  of  the 
fathers. 

The  progeny  of  the  harlot,  Bell  Juke,  is  a  dreary  monot- 
ony of  harlotry  and  licentiousness  to  the  fifth  generation. 
Two  in  the  fourth  generation  there  are,  and  two  in  the  fifth, 


Geography  of  Man  in  Relation  to  Eugenics  307 

against  whom  there  is  nothing  and  their  progeny  mostly 
moved  to  another  neighborhood  and  are  lost  sight  of. 
Very  likely  they  have  married  into  stronger  strains  and  are 
founders  of  reputable  families. 

The  progeny  of  Erne  Juke  and  the  son  of  Max  (a  thief) 
show  to  the  fifth  generation  a  different  aspect.  Some  larceny 
and  assault  there  are,  and  not  a  little  sexual  immorality,  but 
pauperism  is  the  prevailing  trait. 

Thus,  in  the  same  environment,  the  descendants  of  the 
illegitimate  son  of  Ada  are  prevailingly  criminal;  the  pro- 
geny of  Bell  are  sexually  immoral;  and  the  offspring  of 
Efne  are  paupers.  The  difference  in  the  germ  plasms  deter- 
mine the  difference  in  the  prevailing  trait.  But  however 
varied  the  forms  of  non-social  behavior  of  the  progeny  of 
the  mother  of  the  Juke  girls,  the  result  was  calculated  to 
cost  the  state  of  New  York  over  a  million  and  a  quarter  of 
dollars  in  seventy-five  years — up  to  1877,  and  their  proto- 
plasm has  been  multiplied  and  dispersed  during  the  subse- 
quent thirty-four  years,  and  is  still  going  on. 

The  Ishmaelites. — As  another  example  of  a  great  family 
tracing  back  to  a  single  man  may  be  taken  "The  Tribe 
of  Ishmael"  of  central  Indiana,  as  worked  out,  under 
the  direction  of  Rev.  Oscar  C.  McCulloch,  of  the  Charity 
Organization  Society,  Indianapolis.  The  progenitor  of  this 
tribe,  Ben  Ishmael,  was  in  Kentucky  as  far  back  as  1790, 
having  come  from  Maryland  through  Kentucky.  One  of 
the  sons,  John,  married  a  half-breed  woman,  and  came  into 
Marion  County,  Indiana,  about  1840.  His  three  sons  who 
figure  in  this  history  married  three  sisters  from  a  pauper 
family  named  Smith.  They  had  altogether  fourteen  chil- 
dren who  survived,  sixty  grandchildren,  and  thirty  great- 
grandchildren, living  in  1888. 


308  Heredity  and  Eugenics 

Since  1840,  this  family  has  had  a  pauper  record.  They  have  been 
in  the  Almshouse,  the  House  of  Refuge,  the  Woman's  Reformatory, 
the  penitentiaries,  and  have  received  continuous  aid  from  the  town- 
ships. They  are  intermarried  with  the  other  members  of  this  group, 
....  and  with  over  two  hundred  other  families.  In  this  family 
history  are  murders,  a  large  number  of  illegitimacies,  and  of  prostitutes. 
They  are  generally  diseased.  The  children  die  young.  They  live 
by  petty  stealing,  begging,  and  ash-gathering.  Iri  summer  they 
"gypsy"  or  travel  in  wagons,  east  or  west.  We  hear  of  them  in 
Illinois  about  Decatur  and  in  Ohio  about  Columbus.  In  the  fall 
they  return.  They  have  been  known  to  live  in  hollow  trees,  on  the 
river  bottoms  or  in  empty  houses.  Strangely  enough,  they  are  not 
intemperate  to  excess. 

Ah,  that  in  the  hordes  pressing  at  the  gate  at  Ellis 
Island,  we  could  distinguish  the  John  Prestons  from  the 
Ben  Ishmaels  of  the  future! 

THE  EUGENICS  MOVEMENT 

Since  the  time  of  Plato  there  have  not  been  lacking 
persons  who  have  urged  that  the  human  race  would  be 
improved  were  more  attention  paid  to  marriage  matings. 
But,  in  recent  years,  these  ideas  have  become  so  widespread 
and  have  been  urged  with  such  vigor,  as  to  warrant  us  in 
speaking  of  a  present  eugenics  movement.  There  are  two 
chief  impulses,  it  seems  to  me,  for  this  modern  movement, 
both  world- wide.  The  first  of  these  is  a  conviction  that 
there  is  a  great  proportional  increase  in  feeble-mindedness 
in  its  numerous  forms — a  great  spread  of  animalistic  traits— 
and  of  insanity.  When  a  state  like  New  York  spends  one- 
seventh  of  its  state  income  for  the  care  of  the  insane  it  is 
not  strange  that  many  of  its  citizens  are  inquiring  why  this 
is  and  whether  there  is  any  end  to  the  increasing  proportion 
of  the  state's  income  that  must  be  spent  in  caring  for  those 
who  cannot  aid  themselves.  The  proportion  of  those  who 
are  feeble-minded  in  such  various  directions  as  to  constitute 


Geography  of  Man  in  Relation  to  Eugenics  309 

the  feeble-minded  class  is  estimated  at  3  per  cent  of  our 
population,  and  were  we  to  include  drunkards,  paupers, 
grave  sex-offenders,  the  criminalistic,  the  insane,  and  those 
with  innate  physical  weaknesses  that  render  them  for  the 
most  part  incompetent,  it  seems  a  safe  estimate  that  8 
per  cent  of  our  population  are  far  from  having  the  capacities 
of  effective  men  and  women,  able,  not  merely  to  support 
themselves,  but  really  to  push  forward  the  world's  work. 
The  cost  of  caring  for  those  who  cannot  care  for  themselves 
because  of  their  bad  breeding  is  very  heavy — perhaps  two 
hundred  million  or  more  a  year.  A  study  of  the  cause  of 
the  increase  of  dependents  indicates  that  it  is  because  the 
birth  rate  of  the  better  classes  is  constantly  falling;  a  Har- 
vard class  does  not  reproduce  itself  and  at  the  present  rate, 
one  thousand  graduates  of  today  will  have  only  fifty  descend- 
ants two  hundred  years  hence.  On  the  other  hand,  recent 
immigrants  and  the  less  effective  descendants  of  the  earlier 
immigrants  still  continue  to  have  large  families;  so  that 
from  one  thousand  Roumanians  today  in  Boston,  at  the 
present  rate  of  breeding,  will  come  a  hundred  thousand  two 
hundred  years  hence  to  govern  the  fifty  descendants  of 
Harvard's  sons!  Such  facts  as  these  have  awakened  the 
people  to  a  sense  of  the  omnipotence  of  human  breeding. 

The  other  impulse  is  the  spread  of  knowledge  of  the 
modern  principles  of  heredity;  and  an  appreciation  of  the 
facts,  first,  that  they  afford  a  clear  method  in  detail  for 
improving  the  blood  of  the  nation,  and,  secondly,  that  the 
results  of  this  study  can  be  set  forth  so  simply  and  clearly 
that  they  may  become  a  part  of  our  social  idealism  and  may 
serve  to  point  the  way  to  useful  legislation.  Heredity  will 
save  the  people  from  the  perdition  that  is  to  come. 

The  realization  of  this  fact  has  led  to  activity  in  various 
directions.  In  Germany,  an  International  Society  of  Race 


310  Heredity  and  Eugenics 

Hygiene  has  been  organized  and  in  England  exists  a  Eugen- 
ics Education  Society  which  publishes  the  Eugenics  Review, 
and  is  organizing  an  International  Congress  of  Eugenics  for 
1912.  The  Eugenics  Education  Society  has  fostered  the  for- 
mation of  several  branches  in  the  United  Kingdom.  For 
some  years  Francis  Galton  maintained  a  Eugenics  Labo- 
ratory, directed  by  Professor  Karl  Pearson,  that  has  pub- 
lished a  valuable  Treasury  of  Human  Inheritance,  and  was 
lately  well  endowed  at  his  death. 

In  America  one  of  the  first  undertakings  in  Eugenics 
was  that  of  Dr.  Alexander  Graham  Bell,  who  was  much 
impressed  by  the  consequences  of  marriages  of  the  deaf  in 
America.  He  founded  the  Volta  Bureau  in  Washington, 
which  contains  extensive  records  of  the  deaf. 

In  1881  Mr.  Loring  Moody,  of  Boston,  who  was  the 
organizer  of  the  Association  for  the  Prevention  of  Cruelty 
to  Children  and  assisted  in  the  foundation  of  the  Asso- 
ciation for  the  Prevention  of  Cruelty  to  Animals,  organized 
an  Institute  of  Heredity,  but  his  death  soon  after  brought 
his  plans  to  naught. 

In  October,  1910,  there  was  started  at  Cold  Spring 
Harbor  on  Long  Island,  the  Eugenics  Record  Office,  which 
seeks  to  be  a  clearing-house  for  data  on  human  blood  lines 
in  America.  It  has  collected  several  hundred  records  of 
family  traits  and  made  extensive  studies  into  the  pedigrees 
of  the  feeble-minded,  epileptic,  paupers,  and  insane.  This 
office  is  publishing  a  Bulletin.  In  time  we  shall  have  there, 
we  expect,  data  that  will  be  useful  to  those  contemplating 
marriage.  In  various  directions  we  hope  to  play  an  impor- 
tant part  in  creating  a  sentiment  and  a  knowledge  that 
shall  lead  to  the  improvement  of  the  blood  of  the  American 
people. 


INDEX 


INDEX 


Albinism,  278 
Alcoholism,  285 
Amphibians,  211 
Appetency,  10 
Ascaris,  45 

Bacteria,  work  with,  202 
Bateson,  W.,  work  of,  170 
Beetles,  work  with,  181,  213,  216 
Biffen,  R.  H.,  work  of,  124 
Bigelow,  Mabel,  pedigree  of,  302 
Bigelow,  Melville  M.,  pedigree  of,  302 
Biometry,  16 
Breckinridge,  Robert,  Col.,  pedigree  of, 

3°4 

Brown,  John,  Rev.,  pedigree  of,  304 
Buchanan,  R.  E.,  work  of,  203 
Burbank,  Luther,  work  of,  130 

Capsella,  work  with,  203 

Carman,  E.  S.,  work  of,  130 

Carow,  Edith  Kermit,  pedigree  of,  302 

Castle,  William  E.,  39,  62;  work  of, 
112,  149 

Characters,  coupled  and  antagonistic. 
101;  nulliplex,  271;  positive,  nega- 
tive, duplex,  270 

Chickens,  work  with,  146 

Chromatin,  26 

Chromosomes,  26,  45,  66,  287 

Churchill,  Winston,  pedigree  of,  302 

Citrus  fruit,  work  with,  128 

Clay,  Henry,  pedigree  of,  304 

Correns,  C.  E.,  work  of,  41 

Coulter,  John  M.,  3,  22 

Cu6not,  work  of,  65 

Custis,  George  Washington  Parke, 
pedigree  of,  303 

Cytoplasm,  24 


Daphnia,  work  with,  210 

Darwin,  Charles,  work  of,  39,  142,  168 

Darwin,  Erasmus,  9 

Davenport,  C.  E.,  269,  289;   work  of, 

149 

Davis,  B.  M.,  work  of,  199 
Deaf-mutism,  280 
Dementia,  283 

Deming,  Elizabeth,  pedigree  of,  302 
Determiner,  269;  absence  of,  279 
DeVries,  Hugo,  work  of,  41,  170 
Dihybrids,  93 
Dominance,  105 
Drosophila,  work  with,  75,  213 
Dwight,  Sereno  Edwards,  pedigree  of, 

3°i 
Dwight,  Theodore  William,  pedigree  of, 

302 
Dwight,  Timothy,  pedigree  of,  301 

East,  Edward  Murray,  83,  113 

Edwards,  Jonathan,  pedigree  of,  301 

Edwards,  Richard,  pedigree  of,  301 

Edwards,  Timothy,  pedigree  of,  301 

Egg,  31,  45 

Emerson,  R.  A.,  work  of,  101 

Environment,  9 

Epilepsy,  282 

Eugenics,  269,  286;  geography  of  man 
in  relation  to,  289;  organization  of 
movement,  308;  in  relation  to  migra- 
tions, 294 

Evolution,  conception  of,  4;  explana- 
tion of,  7;  fact  of,  5;  method  of,  39; 

Eyes,  inherited  characters,  270,  276 

Feeble-mindedness,  280 
Fitzhugh,   William   Col.,   pedigree   of, 
303 


3*4 


Heredity  and  Eugenics 


Gager,  C.  S.,  work  of,  205,  208,  222 

Gallon,  F.,  work  of,  16 

Gametes,  29,  62,  87,  141 

Gametophyte,  34 

Gates,  Merrill  Edward,  pedigree  of,  302 

Gates,  R.  R.,  work  of,  199 

Genetics,  83 

Genotype,  no 

Geography,  in  relation  to  eugenics,  289 

Germ  plasm,  141;   direct  modification 

of,  165;   influence  of  the  single,  300; 

sudden  transmutation  in,  167 
Goethe,  work  of,  9 
Guinea-pigs,  work  with,  42,  149 
Guthrie,  C.  G.,  work  of,  146 

Hair,  characters  of,  272 

Henry,  Patrick,  pedigree  of,  304 

Heredity,  17,  42,  289;  and  sex,  62 

Heterozygote,  62 

Heydt,  Hans  Jorst,  pedigree  of,  298 

Homozygote,  62 

Howard,  Benjamin,  pedigree  of,  304 

Hoyt,  Simeon,  pedigree  of,  297 

Human  breeding,  relations  of  barriers 

to,  289 

Hybridization,  118 
Hybrids,  91,  122,  166 

Inheritance,  42,  83,  141;    sex-limited, 

287 

Insanity,  283 
Insects,  work  with,  212 
Ishmaelites,  the,  pedigree  of,  307 

Johannsen,  W.  L.,  work  of,  85,  no 
Jukes,  the,  pedigree  of,  305 

Kammerer,  work  of,  211 

Kentucky  aristocracy,  pedigree  of,  304 

Klebs,  G.,  work  of,  204 

Knight,  Thomas,  work  of,  84 

Kolreuter,  work  of,  84 

Lamarck,  work  of,  10 

Latency,  97 

Lee,  Francis  Lightfoot,  pedigree  of,  303 


Lee,  Richard,  pedigree  of,  303 
Lee,  Richard  Henry,  pedigree  of ,  303 
Lee,  Robert  E.,  pedigree  of,  303 
Leptinotarsa,  work  with,  181,  216 
Lutz,  work  of,  213 

MacDougal,  D.  T.,  work  of,  205,  222 

Macro-gamete,  64 

Maize,  work  with,  54,  85,  116 

Man,  inheritance  of  physical  and 
mental  traits  of,  269 

Manhattan  Island  and  eugenics,  296 

Mendel,  Gregor,  work  of,  18,  40 

Mendelism,  18,  40,  85,  100,  104 

Mice,  work  with,  212 

Micro-gamete,  64 

Migrations,  and  their  eugenic  signifi- 
cance, 294 

Minot,  Charles  Sedgwick,  pedigree  of, 
302 

Monohybrids,  9; 

Morgan,  T.  H.,  work  of,  75,  222 

Mutation,  13,  170 

Naegeli,  Karl,  work  of,  40 
Natural  selection,  1 1 
Neo-Darwinians,  168 
Nereis,  work  with,  47 
New  England  and  eugenics,  296 
Nitrogen,  in  soil,  120 
Nucleus,  24 

Oenothera,  work  with,  172,  197 
Oranges,  work  with,  128 
Orthogenesis,  14 
Orton,  W.  A.,  work  of,  125 

Paine,  Robert  Treat,  pedigree  of,  302 

Pangenesis,  142 

Parthenogenesis,  67 

Patton,  Elizabeth,  pedigree  of,  304 

Pauperism,  285 

Pearson,  Karl,  work  of,  16 

Phosphorus,  in  soil,  1 20 

Plant  breeding,  113 

Potassium,  in  soil,  120 


Index 


315 


Preston,  John,  pedigree  of,  304 
Price,  H.  L.,  .work  of,  125 
Pringsheim,  N.,  work  of,  203 
Protoplast,  24 
Punnett,  R.  C.,  work  of,  66 

Reeve,  Sarah  Tapping,  pedigree  of,  301 

Reichert,  work  of,  224 

Reproduction,  power  of,  23;  sexual,  29; 

by  spores,  29 

Richardson,  Ann,  pedigree  of,  302 
Riley,  C.  V.,  work  of,  65 
Russo,  work  of,  65 

St.  Hilaire,  Geoffrey,  work  of,  9 

Saltation,  171 

Schenk,  work  of,  65 

Sedgwick,  Catherine  Maria,  pedigree  of, 

302 

Selection,  118,  131 
Sempervivum,  work  with,  204 
Sex,  and  heredity,  62;  immorality,  285 
Shamel,  A.  D.,  work  of,  124 
Skeleton,  inherited  characters  of,  277 
Soil,  1 20 

Sparks,  Jared,  pedigree  of,  301 
Sperm,  31,  45 
Sporophyte,  34 

Stoughton,  Abigail,  pedigree  of,  302 
Sumner,  F.  B.,  work  of,  210,  212 
Swimming  spores,  29 
Synthesis  of  a  mutating  race,  182 

Talcott,  Mary,  pedigree  of,  301 
Thomsen's  disease,  278 
Tobacco,  work  with,  114 
Tower,  William  Lawrence,  141 
Treat,  Mary,  work  of,  65 


Tschermak,  E.,  work  of,  41 
Tuttle,  Elizabeth,  pedigree  of,  300 
Tyler,  Daniel,  pedigree  of,  301 

Unit-character,  48 
Use  and  disuse,  10 

Variation,  germinal  in  animals,  210; 
in  Chrysomelid  beetles,  213;  by  com- 
bined selection  and  hybridization, 
234>  by  different  forces,  200;  by 
hybridization,  231;  origin  of,  144; 
peripheral  origin  of,  143;  in  plants, 
202;  by  selection,  238;  somatic, 

'45 

Vilmorin,  P.,  work  of,  84 

Vincent,  Marvin  Richardson,  pedigree 

of,  302 
Virginia      and     eugenics,     295;      first 

families,  of  303 
Von  Riimker/work  of,  125 

Waite,  Morrison,  pedigree  of,  302 
Washington,  George,  pedigree  of,  304 
Webber,  H.,  work  of,  125,  128 
Weismann,  A.,  work  of,  41,  no,  168 
Whitney,  Henrietta  Frances,  pedigree 

of,  302 

Wilson,  E.  B.,  work  of,  47 
Woltereck,  work  of,  210 
Woolsey,   Theodore   Dwight,   pedigree 

of,  301 

Yeasts,  work  with,  202 

Zedebauer,  E.,  work  of,  203 
Zoospore,  29 
Zygote,  30,  62 


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